THE SPECTROGRAPH

George R. Harrison Spectroscopy LaboratoryMassachusetts Institute of Technology

Volume 21, Number 2 Spring 2005

Personality: Robert FieldResearch Report:Electronic and Rotational Motionsin CaFResearch Report:Real-Time SpectralDiagnosis using TMSSpring Seminar:Modern Optics and SpectroscopyApril 12 WorkshopOptical Imaging of Pre-Cancerin the EsophagusSpectral Lines:Archimedes’ Solar Weapon

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Also in this issue

Robert Field to give LordLecture on April 26

Robert Field, a Professor of Chemis-try at MIT, has been selected as the2005 Lord Lecturer. He will speak onApril 26 on the topic “Just SmallEnough”. Dr. Field, a physical chemist, has along and distinguished research careerin studies of perturbations in the spec-tra of diatomic molecules, and he haspioneered in the development of nu-merous optical methods to probe thestructure and dynamics of molecules.He is also the inventor of the techniqueof stimulated emission pumping, awidely used method for studying theelectronic structure of molecules. Now in its fourteenth year, the LordLecture commemorates the achieve-ments of Richard C. Lord, a pioneer ininfra-red and biochemical spectros-copy and director of the SpectroscopyLaboratory for 30 years. Each year’slecturer is selected by a committee ofchemists, physicists and engineers atMIT who are active in various fields ofspectroscopy. Past recipients includeWatt Webb, Charles Townes, CarlLineberger, Steven Chu, and BrittonChance.A biographic sketch of Dr. Field can befound on page 2.

On February 28, 2005 the Center for LaserTechnology/Laser Technology Program atthe Indian Institute of Technology (IIT),Kanpur created a distinguished lecture se-ries in honor of Dr. Ramachandra Rao Dasari,Associate Director of the SpectroscopyLaboratory. The inaugural function was aday long program of talks from professorsand senior scientists who were former IIT,Kanpur graduates and a poster session fromthe current students of IIT, Kanpur. Dr.Dasari spoke on “Spectroscopy for diag-nosis of disease”. In each subsequent year

Spectroscopy Laboratory toGet New Physical Plant

Dasari Honored at IndianInstitute of Technology, Kanpur

Dasari, continues on page 3

Ramachandra DasariRobert Field

The Spectroscopy Laboratory will un-dergo a complete renovation over the next18 months and aquire a new physical plant.The new laboratories and offices will be lo-cated in Bldg. 6, adjacent to the present lo-cation in Bldg. 6A. The architectural designof the 10,000 sq. ft. of new research space,with a total of 14 laboratories and two smallservice facilities for chemical preparationand cell culture, reflects the research direc-tions set forth in the Laboratory’s 20 yearresearch plan. The Laboratory last under-went renovation in 1980. The current Spectroscopy Laboratorybuilding, Bldg. 6A, was designed in 1928by Karl T. Compton, MIT’s ninth president,and George R. Harrison. As a centerpieceof the newly reconstituted Physics Depart-ment, President Compton wanted to createa modern laboratory dedicated to spectros-copy and devoted much personal attentionto the construction details. In an article de-scribing the construction of the Spectros-copy Laboratory, Compton wrote that thebuilding “expresses a definite convictionthat the science of spectroscopy is destinedin the future to play a role of increasing im-portance in bringing about an understand-ing of the electrical structure of atoms andmolecules and the interatomic and molecu-lar forces which underlie the interpretationof physical and chemical phenomena.” [1,2]The 13 room Spectroscopy Laboratory wascompleted in 1930, a full year ahead of theEastman Laboratories (Bldg. 6). A key fea-ture was a 10 m by 10 m walk-in spectrographfor long optical path length studies of weakspectral lines with high resolution. (Figs. 1-3). This building is believed to be the firstbuilding constructed exclusively for thepurposes of spectroscopy. Building 6A has housed the SpectroscopyLaboratory for 75 years. It is a remarkable

Rennovations, continues on page 6

THE SPECTROGRAPHPublished by the George R. Harrison Spec-troscopy Laboratory at the MassachusettsInstitute of Technology, Cambridge, MA02139-4307. Comments, suggestions, and in-quiries can be directed to the editor.Editors: Tim Brothers, Jenna PicceriStaff: Zina Queen

GEORGE R. HARRISONSPECTROSCOPY LABORATORYDirector: Michael S. FeldAssociate Director for ScientificCoordination:

Jeffrey I. SteinfeldAssociate Director:

Ramachandra R. DasariThe Spectroscopy Laboratory houses two laserresearch resource facilities. The MIT LaserResearch Facility, supported by the NationalScience Foundation, provides shared facilitiesfor core researchers to carry out basic laser re-search in the physical sciences. The MIT La-ser Biomedical Research Center, a National In-stitutes of Health Biomedical Research Tech-nology Center, is a resource center for laserbiomedical studies. The LBRC supports coreand collaborative research in technological re-search and development. In addition, it pro-vides advanced laser instrumentation, along withtechnical and scientific support, free of chargeto university, industrial, and medical research-ers for publishable research projects. Call orwrite for further information or to receive ourmailings.(617) 253-4881http://web.mit.edu/spectroscopy

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Personality

Robert Field

Robert Field Robert Field grew up in Chicago. Hisearliest memories involve 78 rpm records(Leadbelly) and food (bacon), not chem-istry, although his father Edmund was aphysical chemist (totally innocent of quan-tum mechanics) at Standard Oil of Indi-ana. He remembers dissolving in tearswhen his mother Kay excitedly told himthat he had “broken a record”, unaware ofthe distinction between black vinyl andaccomplishments.

The mid 1950’s was too late to obtain theingredients for explosives from chemistrysets, so Robin (that was his pre-Bob nick-name) started a notebook describing thecolors he was able to generate with hissafety-minded chemicals. A budding spec-troscopist! In sixth grade he made whatwas probably the most important transi-tion of his life, from the Chicago PublicSchools to the University of Chicago Labo-ratory School, where the teachers seemedto be genuinely interested in the ideas oftheir students. There were many greatteachers at the Lab school, and of courseone of them was a chemist. Bob majored in chemistry at Amherst Col-lege, working with an inorganic chemist,Cooper Langford, who “set the hook” bydoing a group theoretical derivation of aselection rule on a scrap of paper. ButBob’s interest in spectroscopy was bornduring two summers in the inert gas fluo-ride group at Argonne National Labora-tory, where he recorded and attempted tointerpret proton and fluorine NMR spec-tra of SbF5 in anhydrous HF. His AmherstThesis was on UV and NMR spectra of Pdcomplexes of aniline (which he remembersdistilling outside of a hood). Bob’s application to graduate schoolspecified theoretical inorganic chemistryas his area of interest. By accident (orextraordinary good luck!) Bob ended upin Bill Klemperer’s research group atHarvard University, where his interest inspectroscopy grew into a passion for smallmolecules, multiple resonance spectros-copy, spectroscopic perturbations, andother arcanae. His thesis project, measure-ment of the electric dipole moment of theCO A1Π state by radiofrequency-optical(pre-laser!) double resonance (RFODR),was a failure. However, his fits of all extantspectroscopic data on the excited valencestates of CO, intended as a basis for pre-dicting the ∆-doublet transition frequen-cies he needed for his RFODR-Stark effectexperiment, became the foundation of hisscientific career. This takes the familiarstory of a warm-up project becoming theThesis project to a new level! His book,“Perturbations in the Spectra of DiatomicMolecules” and its sequel, “The Spectraand Dynamics of Diatomic Molecules”, hisinterest in semi-empirical models built onmatrix element quantum number scalingrules (both atomic-ion-in-molecule ligandfield theory and multichannel quantumdefect theory for e–<−>MX+ scattering),

and his optimism that an elegant simplicityis hidden behind the apparent complexityof a spectrum, all grew naturally out of hispre-thesis warm-up project. Bob’s first project as a postdoc at theUniversity of California at Santa Barbarawith Herb Broida and David Harris was torecord microwave optical double reso-nance spectra of BaO. This laser counter-part of his RFODR Thesis project workedwithin two weeks of his arrival at UCSB,providing wonderful compensation for 6years of failure at Harvard. BaO and all ofthe alkaline earth monoxide andmonohalide molecules quickly joined COas Bob’s favorite molecules because theygave him a new use for his beloved spec-troscopic perturbations. The chemilumi-nescent Ba + N2O reaction had a >30%quantum yield for BaO in the metastablea3Π electronic state. The perturbed levelsact as a funnel through which populationmust flow en route to levels of the A1Σ+

state that can fluoresce to the X1Σ+ groundstate. The (short-lived) excitement overthe possibility of building an electronictransition chemical laser based on the BaOa3Π~A1Σ+ perturbations contributed toBob’s invitation to join the MIT faculty asAssistant Professor of Chemistry in 1974. Bob’s favorite description of his MIT re-search is “spectroscopy beyond molecu-lar constants.” Spectra encode dynamicsand the greatest challenge is not to fill jour-nals with archival data but to uncover alarger picture in which coupling mecha-nisms between intramolecular modes arecharacterized. How does energy flow fromone bond to another, from an electron tonuclear vibrations and rotations? Simplemolecules at high levels of internal excita-tion exhibit complex dynamics. The usualsmall-displacements-from-equilibriummodels fail utterly because modes usuallyconsidered as separable are recoupled inunforeseen ways and fundamental con-cepts like chemical bonds and oxidationstates can no longer be relied upon. Whenis a spectrum intrinsically unassignable (er-godic) and when is it merely inconvenientto use traditional assignment and spectro-scopic modeling methods? Are there non-traditional methods to trick molecules intorevealing their dynamical secrets? Two molecules, acetylene and CaF, havebeen the subject of extraordinary experi-mental effort in Bob’s research group.More than 100 person-years have been in-

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a day long program will be held in which adistinguished scientist is honored. Febru-ary 28 is National Science Day in India, aswell as C.V. Raman’s birthday. Dr. Dasari was born and raised in India.He was educated at Benaras Hindu Uni-versity and Alighar Muslim University andis one of the first faculty members to joinIIT, Kanpur at its inception. His connec-tion to MIT dates back to 1966 when hespent two years working in the researchgroup headed by Professor Ali Javan. Hisexperience in lasers gained at that timehelped him to set up one of the largest la-ser laboratories at IIT, Kanpur where la-sers and laser instrumentation was fabri-cated and graduate students trained. Dur-ing that period, as a member of the Univer-sity Grants Commission, he helped improveundergraduate science programs in degree-granting colleges. He was also instrumen-tal in the transfer of laser technology toindustry. He left IIT, Kanpur in 1978, mov-ing to the National Research Center in Ot-tawa for a year and the University of Brit-ish Columbia for another year, before join-ing the MIT Spectroscopy Laboratory in1980. Dr. Dasari has played a major role in theSpectroscopy Laboratory over the past 25years, coordinating research programs andfacility development associated with theNIH supported Laser Biomedical ResearchCenter supported by NIH and the NSF sup-ported Laser Research facility. His researchactivities cover a wide range of disciplines:atomic and molecular physics (cavity-QED,single atom laser, atomic and molecular col-lisions, laser-nuclear studies); chemicalphysics (vibrational-rotational relaxation,Dicke narrowing in infrared transitions, la-ser spectroscopy of rare-earth ions ); clas-sical spectroscopy (high resolution spec-troscopy of simple molecules); surfaceenhanced Raman scattering (single mol-ecule detection); and his relatively largeefforts in the last ten years related to laserbiomedical studies, leading to spectral di-agnosis of disease using techniques includ-ing scattering, reflectance, fluorescence,and Raman spectroscopy. His most recentresearch relates to low coherence interfer-ometry for detecting nanometer motions incells and nerve bundles. His research pub-lications in referred journals number morethan 200 and cover most of the major jour-nals in physics and chemistry.

Dasari, continued from page 1vested in the spectrum of acetylene. Bobdid his first experiments on CaF at UCSB in1973! These molecules are just simpleenough to contain hints of fundamental dy-namical processes in their spectra. Acetylene (and its molecularly impover-ished cousins HCN and HCP) can undergo

bond-breaking isomerization to C CHH

vi-

nylidene and, because vinylidene is the tran-sition state for Ha C1 C2 Hb<−>Hb C1 C2 Haidentical atom permutations, permutationsplittings in the symmetric double minimumacetylene potential energy surface selec-tively label the highly excited vibrationallevels that sample the minimum energyisomerization path. This is a novel way torecognize the isomerization-relevant fea-tures in a spectrum without attempting tomake secure vibrational assignments of ev-ery observed transition. This is an uncon-ventional, and still not achieved, spectro-scopic (rather than chemical kinetic) way tocharacterize a “transition state”. CaF is the sodium atom of diatomic mol-ecules. It contains one electron outside theCa2+ and F– closed-shell atoms. The detailsof the CaF Rydberg spectrum reveal themechanisms of a light electron undergoinginelastic scattering off of two heavy nuclei,just as the Rydberg spectra of Na reveal thebeyond-hydrogen mechanisms of an elec-tron scattering off of a round but space-filling Na+ nucleus. Of course the e–ΣCa2+F–

scattering is much more complicated and thedynamics much richer than the e–ΣNa+ scat-tering. The goal, says Bob, which seemswithin grasp, is to obtain a complete dy-namical picture, including dissociation andionization processes, expressed in the formof an internuclear distance dependent quan-tum defect matrix, µ(R). Frequency-domain spectroscopists arecollectors of eigenstates. Eigenstates arestationary, i.e. a molecule in an eigenstatedoes not move, but eigenstates encode dy-namics. The facilitators of the most inter-esting intramolecular dynamics are off-di-agonal matrix elements of the molecularHamiltonian between Born-Oppenheimerbasis states. Bob was amused to discoverthat, from his very first experiments in theKlemperer group, he was studying dynam-ics. Throughout his career, he has attemptedto discover new ways that dynamics areencoded in spectra and new ways to recordspectra that are uniquely selective to spe-cific classes of intramolecular dynamics.The game is still afoot.

Archimedes’ Solar Weaponby Stephen R. Wilk

Spectral Lines

The Discovery Channel’s seriesMythbusters, on cable TV features a groupof Hollywood special effects experts runningtests and demonstrations to verify or dis-prove “urban legends” and odd reports. Anepisode of their second season, first broad-cast in September 2004, they examined thecase of Archimedes’ Mirror. Archimedes is the third century B.C.E.mathematician and engineer from Syracusein Sicily. Only a few of his works have comedown to us, but those seem remarkably aheadof their time. In The Sand ReckonerArchimedes outlines a system for writingvery large numbers, much like our system ofexponentials, and then goes on to calculatehow many grains of sand it would require tofill the universe. His work On Floating Bod-ies gave us Archimedes’ Principle, that theweight of a body placed in water is lessenedby the weight of water displaced. From hiswork on the circle he obtained a value of pibetween 3 10/71 and 3 1/7. Archimedes was also supposed to havecreated exotic weapons for Hiero II, the rulerof Syracuse, for use against the Romansduring the Second Punic War. Of all the weap-ons used – catapults, siege towers, giantcranes – the most interesting is a giant mir-ror or collection of mirrors said to have beenused to burn enemy ships. Lucian ofSamosota and Galen both mention this, asdoes the sixth century architect of He HagiaSophia (usually called Saint Sophia),Anthemius of Tralles, who wrote thatArchimedes employed many mirrors. Proclus,a noted mathematician, was said to have alsoused burning mirrors against Vitellius in 514C.E. Can the story be true? The Mythbustersteam investigated, going so far as to build asection of an ancient boat and manufactur-ing a sort of giant Fresnel mirror out of indi-

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Stephen Wilk

Personality,continued from page 7

vidual mirrors measuring about a footsquare, placed on a large plywood back-ing. A depth gauge was used to adjust thetilt of each mirror segment. The resultinggiant mirror focused sunlight onto an areaabout 2-3 feet in diameter on the section ofa ship, located perhaps 100 feet away. Al-though the illuminated spot got warmer, itdidn’t get hot enough to burn, and theyconcluded that, in the words of the show,“The myth was busted!” I addition to theirfailure, they cited the unlikely conditions –you’d need a sunny day to use the solardeath ray, and an enemy willing to attackthen[1,2]. But was the test fair? The use of the crudefocusing mechanism meant that the beamwas not optimally focused. If some opticalmeans had been used rather than mechani-cal means, would they have been able tokindle a fire? Twenty two years ago Albert C. Claus ofLoyola University suggested thatArchimedes could have performed his featif he had a team of soldiers armed with mir-rors, each of which could be independentlypointed [3]. He even proposed a method ofpointing each mirror in the array[4]. O. N.Stavroudis wrote back to note that the ideaof using burning mirrors against one’s en-emies predates Archimedes, and can befound in Aristophanes’ comedy TheClouds (produced in 423 B.C.E.). Further-more, all the sources for Archimedes’ featdate from centuries after his time. If therewas no credible account of the event, whyshould we believe that it happened[5]? As K.D. Mielenz pointed out, it appearsthat the experiment had been done before– George Louis leClerc, Comte Buffon , fa-mous for his “dropping needles” statisti-cal method for determining the value of pi,had performed a very similar experiment[6].Buffon assembled 168 mirrors 8 inches by10 inches in dimension, adjusted to pro-duce the smallest possible image 150 feetaway. The array turned out to be a formi-dable weapon. At a distance of 66 feet, 40mirrors ignited a creosoted plank and at 150feet, 128 mirrors ignited a pine plank in-stantly. In another experiment, 45 mirrorsmelted six pounds of tin at 20 feet. Further-more, in 1973 a Greek scientist, IonannisSakkas, got a team of 60 soldiers together,gave each a mirror, and had them direct thesun’s rays at a boat 160 feet away. Theysucceeded in setting the boat afire. The in-cident was reported around the world, in

the London Times, Time magazine, and theNew Scientist[7]. D.L. Simms wrote critiques of the issue,concluding that it was not reasonable tobelieve that this was possible. Simms notesthe work of Sakkas and Buffon, yet con-cludes rather surprisingly that it is irrelevant,since it represents a “static situation”, andthat it is difficult to adjust the focus prop-erly under “battlefield” conditions[8]. Yetthe focusing method suggested by Clausin that first Applied Optics report would giveprecisely the means to maintain a focus ona moving object – it’s not necessary to knowwhat focal length is required, as long aseach independent element is capable oftracking the target.

Archimedes’ Mirror Archimedes’ mirror has shown up in text-books on adaptive optics as the earliest re-corded case of a “rubber mirror”[9]. MichaelLahanas’ website [7]cites a 2002 experimentin Germany in which 500 volunteers used45 cm x 45 cm mirrors to ignite the sail of aship at a distance of 50 meters. The testconditions seem very similar to those usedon the Mythbusters show, except perhapsin using the sail rather than the hull of theship as a target. The only other differenceseems to be the use of volunteers for activefocusing. It’s not clear whether or not Archimedes(or Proclus, or anyone else) ever actuallyused solar mirrors as a weapon of war, but itseems very likely that they could have beenused succesfully [10].

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References

1.Mythbusters Pictures Season 2, Episode16, first broadcast September 29, 2004:ht tp : / /dsc .discovery.com/fansi tes /mythbusters/photogalleries/season_02/season_02.html2. More Mythbusters pictures: http://dsc.discovery.com/fansites/mythbusters/

p h o t o g a l l e r i e s / s e a s o n _ 0 2 /season_02_02.html3. Claus, A. C. “On Archimedes’ Burn-ing Glass”, Applied Optics 12 (10), A14(1973).4. In 1942 L.L. Young of the National Bu-reau of Standards and W.M. Potter of Gen-eral Electric developed the method of aim-ing a heliograph described by Claus in hisarticle. It was incorporated into signallingkits intended for downed pilots manufac-tured by GE. It is described in two articlesby R. S. Hunter: J. Optical Society ofAmerica 35, 805 (1945); “Heliographic Sig-naling Mirrors”, by R.S. Hunter in J. Opti-cal Society of America 36 (2), 110-115(1946). The same method of signalling wasused in Hal Clement’s science fiction novel“Cycle of Fire”, (1957). Arthur C. Clarkedescribed a similar situation in his shortstory, “A Slight Case of Sunstroke”, whichappeared in Galaxy Science Fiction in Sep-tember, 1958. It subsequently appeared inhis collection of short stories, “Tales ofTen Worlds” (1962). A Webpage perform-ing the calculations is: http://zebu.uoregon.edu/~dmason/probs/therm/dyn/sunstrok/sunstrok.html5. Stavroulis, O.N. “Comments on: OnArchimedes’ Burning Glass”, Applied Op-tics 12 (10), A15 (1973).6. Mielenz, K.D. “That Burning Glass”,Applied Optics 13 (5) A14 (1974).7. An excellent site with many referencesis http://www.mlahanas.de/Greeks/Mirrors.htm8. Simms, D.L. “More on That BurningGlass of Archimedes”, Applied Optics 13(5) A16, (1974); at much greater length inD.L. Simms, “Archimedes and the BurningMirrors” of Syracuse, Technology andCulture 18 (1), (1977).9. Hardy, J. W. “Active Optics: A NewTechnology for the Control of Light”, in“Archimedes’ Mirror as Adaptive Optics”,Proc. IEEE 66, 651 (1978); J .E. Pearson inConference on Laser and Electro-OpticalSystems, San Diego CA (1980); both citedin Principles of Adaptive Optics (2nd Edi-tion) R. K. Tyson, Academic Press, 3.10. Archimedes’ Mirror is described in J.D. Walker’s, “The Flying Circus of Phys-ics “(Wiley, 1975) , entry 3.76 on p. 65. Cu-riously, in this heavily-footnoted book,no references to Archimedes Mirror aregiven. In the revised edition, “With An-swers”, published in 1977, some explana-tions are given on p. 247, but without cita-tions.

Archimedes, continued from p3

Interaction between Elec-tronic and Rotational Mo-tions in CalciumMonofluoride

Molecular Rydberg states are interestingfrom a fundamental point of view becausethey allow us to understand, in a ball andspring sense, how energy and angular mo-mentum are exchanged between light elec-trons and heavy nuclei. By their very na-ture, Rydberg series sample electronic mo-tion over a wide range of timescales: alonga Rydberg series, the frequency of elec-tron orbital motion varies from just a fewfemtoseconds (timescale of molecular vi-bration) at low principal quantum numberto tens of picoseconds (timescale of mo-lecular rotation) near the series limit. Byunderstanding how Rydberg series evolvefrom low to high energy, and how differentseries interact with each other, we can un-derstand how electronic, vibrational, androtational motions influence each other ona variety of timescales and identify themechanisms that facilitate intramolecularenergy transfer. The interaction between electronic androtational motion, with which we are con-cerned here, is not a new topic. It has beenstudied since the early 20th century and be-gan with the work of Friedrich Hund, whocategorized molecular electronic states ac-cording to various angular momentum cou-pling schemes, which are now known (anddreaded) as “Hund’s cases”. Hund’s caseshave been used for nearly 80 years to clas-sify electronic states and to define basissets by which complicated dynamical prob-lems may be described. Two of Hund’scases are especially relevant to the descrip-tion of molecular Rydberg states and offerpictorial views of two limiting cases of ro-tation-electron coupling. Energeticallylow-lying Rydberg states typically conformto Hund’s case (b), in which the angularmomentum of the Rydberg electron pre-cesses about the internuclear axis of themolecule under the influence of the cylin-drically-symmetric electric field of the nu-clei. Consequently, neither the orbital an-gular momentum l of the Rydberg electronnor the rotational angular momentum N+ of

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the nuclei (“ion core”) are strictly con-served; only the total angular momentumof the molecule N is a constant of the mo-tion. The two particles interact stronglythrough the electric field of the ion coreand the molecule “rotates as a whole”.When the electrostatic interactions be-tween the Rydberg electron and the ion corebecome sufficiently weak, Rydberg statesconform to Hund’s case (d), in which bothparticles move more or less independentlyof one another. As a result, these Rydbergstates can be described in terms of thequantum numbers of the separate particles;under these circumstances both the orbitalangular momentum l and rotational angu-lar momentum N+ remain well-defined. Despite almost eight decades of researchon the topic, a simple picture of how elec-tronic and rotational motion interact on alltime scales remains elusive. In particular, it

is not clear how electronic and ion-core ro-tational motions influence each other whenthe interactions involved are strong. In thelow-lying Rydberg states of calciummonofluoride, a molecule with a long his-tory in our research group, the electrostaticinteractions between the electron and ionare so strong that these states are very welldescribed in terms of Hund’s case (b) cou-pling. Since the low energy Rydberg statescannot be described in terms of the sepa-rate angular momenta of the separate par-ticles, it is not obvious how these Rydbergseries will evolve with increasing principalquantum number, especially when thebound Rydberg states merge into their re-spective ionization continua. One mightimagine that, as the principal quantum num-ber increases and the time scale of electronicmotion becomes longer and the average dis-

Figure 1. Composition of the pÐ series of CaF as a function of principal quantum numbern. (a) Electron orbital decomposition. (b) Rotational decomposition. Stroboscopicresonances are indicated.

Jeffrey J. Kay, Serhan N. Altunta, Stephen L.Coy, and Robert W. FieldDepartment of Chemistry and G.R. HarrisonSpectroscopy Laboratory, MIT

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tance of the electron from the ion-core be-comes larger, the coupling between the elec-tron and ion should become considerablyweaker. However, as the dipole moment ofthe CaF+ core is on the order of 9 Debye, itwould seem as though electronic and rota-tional motion would be hopelessly en-tangled on all time scales. To generate a ball-and-spring mechanis-tic picture of how electronic and rotationalmotions interact in calcium monofluoride,we have used multichannel quantum defecttheory (MQDT) to calculate molecularwavefunctions for each of the Rydbergstates with principal quantum number n be-tween 5 and 100. To determine the strengthof interactions between electronic and ro-tational motions, we decompose thewavefunctions into their respective angu-lar momenta. This allows us to assess theextent to which the motions of the electronand ion-core influence each other: whenthe wavefunctions can be described in termsof the l and N+ quantum numbers, the in-teraction is weak; where they cannot, theinteraction is strong. Representative re-sults of the calculations are shown in Fig.1. The figure shows the compositions ofsuccessive members of one of the sixRydberg series of CaF as a function of theprincipal quantum number. The decompo-sition in terms of orbital angular momen-tum is shown in (a) and in terms of rota-tional angular momentum in (b). As is evi-dent in the figure, at low principal quantumnumber, where the electron orbits fast rela-tive to the rotational motion of the ion-core,both l and N+ poorly describe the molecu-lar wave functions; the eigenstate wavefunctions have amplitude in several elec-tronic and rotational channels. As the prin-cipal quantum number increases, l and N+

become reasonably good labels: the wavefunctions have amplitude primarily in oneelectronic and one rotational channel. Wethus infer that as electronic motion slows,the electron and ion begin to move inde-pendently. The large features located at n= 45, 55, etc. are examples of “stroboscopic”resonances and occur when the period ofelectron orbital motion is an integer mul-tiple of the period of ion-core rotation.Under such circumstances, the electronsees the ion-core in the same orientationeach time it approaches; the ion-core ap-pears stationary from the point of view ofthe electron. Consequently, at such spe-cial resonances, the angular momenta of thetwo particles become strongly coupled just

as they are at low n. This allows us to de-velop an intuitive mechanistic picture of ro-tational-electronic dynamics valid on all timescales: when electronic and rotational mo-tion are in a stroboscopic relationship toeach other (i.e. “resonant”) the particles in-teract strongly through the anisotropic (axi-ally symmetric) field of the nuclei. Whenthe condition for the stroboscopic reso-nance is not satisfied, the interactions be-tween electron and ion-core “average out”:as shown in Fig. 2, each time the electronapproaches the ion (once per orbit) it is in adifferent orientation. Consequently, the cu-mulative effects of successive electron-ioncollisions cancel one another. In addition to our study of the interactionbetween electronic and rotational motiondescribed here, we are also working boththeoretically and experimentally on otherelectron<−>nuclear energy exchange pro-cesses, especially those that lead to chemi-cal transformations such as dissociationand ionization.

Figure 2. Artist’s conception of dynamicregimes in the high Rydberg states of CaF.Relative timescales of electronic (τKepler) androtational (τRot) motion are indicated beloweach illustration.

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structure that employed the most advancedengineering design and construction tech-niques then available. Great care was takento reduce mechanical and thermal noise. Thebasic design called for an inner building,which housed the research laboratories, andouter building, with an entirely independentfoundation separated by a six inch air gap.The inner research building was designedto float relative to the outer shell, with noconnection between the two. The isolatedfloors of the inner building had an elabo-rate construction, with floors composed ofthree feet of reinforced concrete built uponthe concrete piles. A special isolated floorcovered the concrete base of the outer shell.This floor was mechanically damped usingspecial vibration-absorbing structures builtup in layers of fine sand, roofing felt transitboard, vibration-absorbing cork, and con-crete, and finished with an eight inch rein-forced concrete floor with a smooth cementupper surface. Seismograph tests of thecompleted structure showed that lateral vi-brations were almost completely absent andthat vertical vibrations were very greatlyreduced. In order to minimize the effect of outsidechanges in laboratory temperatures in thebuilding, the entire outside wall of the build-ing was lined with an eight inch layer ofcork embedded between twelve inch ma-sonry walls. Furthermore, the large gratingrooms on the first floor, where constancy oftemperature was most important, were sur-rounded by an additional twelve inch con-crete wall with a six inch air gap. The Spectroscopy Laboratory has a dis-tinguished 75 year history of advances inatomic physics, optics, lasers and spectros-copy. In its early years, the Laboratory be-came famous under Harrison’s leadershipfor its contributions to atomic spectroscopy,including the analysis of complex spectraand qualitative and quantitative analysis ofmaterials. This research eventually resultedin the MIT Wavelength Tables [3]. Duringthe period from 1940 to 1946, many of theLaboratory’s scientists became occupiedwith national defense and war work, andtheir spectroscopic research projects weregradually reduced. During much of this time,the Laboratory’s facilities were used forspectrochemical analysis for the Manhat-tan Project, and many thousands of uraniumsamples collected from the first atomic re-actor at the University of Chicago were ana-

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Figure 3. Ten meter walk-in spectrograph. The instrument was in the form of a Rowlandcircle, a spectrograph that uses a concave grating arrangement to limit light loss due todiffraction.

lyzed with the help of the 10 meter gratingspectrograph. In 1946, Richard C. Lord assumed di-rectorship of the Laboratory. Lord, an ex-pert in infrared and Raman spectroscopy,established both of these areas in the Labo-ratory. Among the scientific achievementsduring this period were discovery and ex-ploitation of the anomalous far-infraredspectra of ring molecules, the first vibra-tional analyses of the laser Raman spectraof proteins, and the important demonstra-tion by Raman spectroscopy that the con-formation of transfer RNA as determinedby X-ray diffraction from a crystallinesample is the same as that in the aqueousmedium existing in living cells.

Also during this period, the interests ofDr. Harrison, now Dean of the School ofScience at MIT, turned to the developmentof spectroscopic instrumentation. In 1949,he invented the echelle spectrograph,which combines very high resolution withbroad spectral range. He developed enginesfor the ruling of diffraction gratings underinterferometric control, by which gratingsof unprecedented size (as large as 400 x600 mm) and optical performance were pro-duced. Several of the laboratories were out-fitted for stable operation of ruling engines,one provided by the Nobel Prize winningphysicist A. A. Michelson. With the arrival of Charles H. Townes andAli Javan in the Laboratory in 1962, thepossibilities of using the recently inventedlaser in spectroscopic research began tobe explored. Townes, awarded the NobelPrize in Physics in 1964 for his contribu-tions in the 1950s to the development ofthe maser and the laser, and Javan, inven-tor the gas laser in 1960, made numerousachievements in the Laboratory, includingthe development of a version of theMichelson-Morley experiment using infra-red lasers, which gave an improved upperlimit on the anisotropy of space, or the ef-fect of “ether drift,” and pioneering stud-ies by Townes and his colleagues of thestimulated Raman and Brillouin effects.Another important achievement was the ob-servation by Javan of the first Lamb dipand its applications to measurement of the1.15 micron Ne20-Ne22 isotope shift. Thisexperiment marked the beginning of the field

Rennovations, continued from page 6

Rennovations, continues on page 8

Figure 2. Original Spectroscopy Laboratory, longitudinal section. From Ref.[2].

Figure 1. Original Spectroscopy Laboratory, first floor plan. From Ref.[1].

Page 8

Rennovations, continued from page 7

A Fond Farewell to Recent GraduatesThe following students who have been associated with the Spectroscopy Laboratory have recently obtained their Ph.D. degrees. We wishthem the best of luck in their future endeavors.

Joshua C. VaughanChemistry, 2005Two-Dimensional Ultrafast Pulse Shapingand its Application to Coherant Controland Spectroscopy

Mirna Jarosz VitasovicChemistry, 2004The Physics and Chemistry of Transport inCdSe Quantum Dot Solids

David W. WardChemistry, 2005Polaritonics: An Intermediate Regime Be-tween Electronics and Photonics

Sungho YoonChemistry, 2004Model Complexes for Active Sites of DiironMetalloproteins: Dioxygen Reactivity andWater Effects

Jaime Dawn ChoiChemistry, 2005Generation of Ultrahigh Frequency Acous-tic Waves for the Characterization of Com-plex Materials

Inhee ChungChemistry, 2004Understanding and Engineering thePhotophysics of Single CdSe Nanocrystals

Joel EavesChemistry, 2004Vibrational Dynamics in Water From themolecule’s Perspective

Christopher FeckoChemistry, 2004Spectroscopic Investigations of HydrogenBond Dynamics in Liquid Water

Abigail HakaChemistry and Medical Physics, 2005Development of In Vivo Raman Spectros-copy for the Diagnosis of Breast Cancer andIntra-Operative Margin Assessment

Munira KhalilChemistry, 2004A Tale of Coupled Vibrations in SolutionTold by Coherent Two-Dimensional Infra-red Spectroscopy

Peter R. PoulinChemistry, 2005Coherant Lattice and Molecular Dynam-ics in Ultrafast Single-Shot Spectroscopy

Nathan StottChemistry, 2004Novel Synthetic Routes to high-Quality II-VI Colloidal Nanocrystals: ControlledGrowth using mild Precursors in the Pres-ence of Selected Ligands

Figure 4. Harrison with the MIT B rulingengine. Using interferometric control, grat-ings of unprecedented size and optical per-formance were produced. The biggest, 400mm x 600 mm, are believed to be among thelargest ruled diffraction gratings ever pro-duced. The MIT B ruling engine is still inuse.

of high-resolution laser saturation spectros-copy. These and other studies made apparentthe importance of lasers to spectroscopyand the study of dynamical processes inatoms and molecules. With the selection ofProfessor Michael S. Feld as Lord’s suc-cessor in 1976, lasers have become a cen-tral research tool of the Laboratory.Achievements during this period includethe first observation of superradiance, thediscovery of a left-handed form of the DNAdouble helix, and the development of stimu-lated emission pumping as a powerful mo-lecular probe. Within this historic framework, the Spec-troscopy Laboratory today continues topursue fundamental and applied researchin a variety of fields. Under Feld’s directiontwo instrumentation resource centers havebeen established to support laser spectro-scopic research in the physical and biomedi-cal sciences. The MIT Laser Research Fa-cility (LRF) is an NSF-supported resourcefor physical science research. The LaserBiomedical Research Center (LBRC), is an

NIH- supported resource for research in bio-medical applications of lasers, light andspectroscopy. The new physical plant willprovide high quality space for the novel re-search directions that it faculty members arepursuing. In the new architectural design, the foun-dation of Bldg. 6A will be the site of a fourstory structure to house the Green Centerfor Physics. During the period of construc-tion, the Spectroscopy Laboratory has beenrelocated to temporary space in BuildingNW-14, the site of the MIT Magnet Labora-tory.

References

1. Compton, K.T., “The New SpectroscopyLaboratory of the Massachusetts Instituteof Technology”, Physica (The Hague) 2,205-210 (1932).2. Compton, K.T., “The George EastmanResearch Laboratories for Physics andChemistry”, Science 75, 472-479 (1932).3. MIT Wavelength Tables (TechnologyPress, Cambridge, 1939).

Seminar on

Modern Optics and SpectroscopySpring Semester 2005

March 8 Mark Johnson, Yale UniversityMark Johnson, Yale UniversityWater at work: Using clusters to understand fundamental aspects ofaqueous chemistry

March 15 Kevin Lehmann, Princeton UniversityCavity ring-down spectroscopy: From gases to cells

March 29 Timothy Zwier, Purdue UniversitySingle conformation vibrational spectroscopy and isomerization dynamics

April 5 Alexander van Oudenaarden, MITHow does a single cell remember

April 12 Elizabeth Nolan, MITSmall molecule fluorescent sensors for imaging zinc in biology

April 19 Jing Kong, MITOrbital spectroscopy and Kondo effect carbon nanotubes

April 26 14th Annual Richard C. Lord LectureRobert Field, MITJust small enough

May 3 Hrvoje Petek, University of PittsburghUltrafast imaging and control of plasma waves in Fermi seas

May 10 Alice Ting, MITFluorescent reporters of protein trafficking and function

Tuesday, 12:00 - 1:00 p.m., Grier Room (34-401)Refreshments served following the seminar.

Sponsored by the George R. Harrison Spectroscopy Laboratory,Department of Electrical Engineering and Computer Science, and School of Science, MIT

Lester Wolfe Workshop in Laser Biomedicine

Optical Imaging of Pre-Cancer in the EsophagusTuesday, April 12, 2005, 4:00-6:00 PM

Massachusetts General HospitalWellman 1 Conference Room

50 Blossom Street, Boston

The incidence of cancer of the esophagus is increasing rapidly in the Western world. Chronic gastroesoph-ageal reflux disease leads to a premalignant change in the esophageal epithelium, known as Barrett’s esopha-gus, and this can progress to dysplasia and adenocarcinoma. The traditional method of detecting these changesemploys endoscopy and taking of multiple biopsies. This workshop will discuss non-invasive optical meth-ods of detecting and monitoring esophageal precancer, including optical coherence tomography, tri-modalspectroscopy and endoscopic confocal microscopy.

Screening and Surveillance of Barrett’s Esophagus: The Challenge, Current Status and OpportunitiesNorman Nishioka, Massachusetts General Hospital and Harvard Medical SchoolUpper Gastrointestinal Optical Coherence TomographyBrett Bouma, Massachusetts General Hospital and Harvard Medical SchoolReal-Time Spectral Diagnosis of Dysplasia in Barrett’s EsophagusJames Tunnell, MIT Spectroscopy LaboratoryEndoscopic Confocal Microscopy for Structure and FunctionGordon Kino, Stanford University

Refreshments served at 3:30 PM

Sponsored by the G.R. Harrison Spectroscopy Laboratory, MIT, MGH Wellman Laboratories, the Harvard-MITDivision of Health Sciences and Technology, and the Center for the Integration of Medicine and Innovative Technology

(Map available online at http://www.cimit.org/images/MGH_Map011305.pdf)

Page 13

Research Article

Real-Time Spectral Diagnosisusing Tri-Modal Spectroscopy

James W. Tunnell, Luis Galindo, SashaMcGee, Jelena Mirkovic, Jonathon Nazemi,Ramachandra R. Dasari, Michael S. FeldGeorge R. Harrison Spectroscopy Laboratory,MITMichael B. WallaceMayo Clinic, Ft. Lauderldale, FLChristian Jost, David Lewin, Stephan WildiMedical University of South Carolina

Kamran BadizadeganMassachusetts General Hospital and G. R.Harrison Spectroscopy Laboratory, MIT

The Spectroscopy Laboratory has beendeveloping real-time spectral diagnosis, anon-invasive method for disease detec-tion. In particular, the Laboratory has re-cently developed a novel spectroscopictechnique, tri-modal spectroscopy orTMS, for the detection of pre-cancers inthe uterine cervix,[1] esophagus,[2] andoral cavity.[3] These feasibility studiesdemonstrate that TMS provides a highlyaccurate diagnosis without the need fortissue removal. Current clinical practice inprecancer detection requires guided inva-sive biopsy, where current guidance pro-cedures are insufficient and biopsies aretime consuming, expensive, and painful.Therefore, TMS offers an exciting oppor-tunity to greatly improve current clinicalpractice by both enhancing biopsy guid-ance and avoiding unnecessary biopsy. In order to leverage the advantages ofspectral diagnosis, instruments and dataanalysis must operate in real-time (i.e. pro-vide a diagnosis within a few seconds).We have recently reported the develop-ment of instrumentation capable of acquir-ing tissue reflectance and fluorescencewithin 1 – 3 seconds.[3, 4] Here, we de-scribe our recent development of “real-time” TMS (< 1 s) spectroscopic algorithmscapable of immediate interpretation of dys-plasia and guided biopsy in patients withBarrett’s esophagus (BE). TMS combines three spectroscopic tech-niques (diffuse reflectance: DRS; intrinsicfluorescence: IFS; and light scattering:LSS) to provide complementary tissue mor-phological and biochemical parameters.DRS analyzes properties of the stromal tis-sue and provides the wavelength depen-dent reduced scattering coefficient, hemo-

globin concentration and oxygen satura-tion.[5] IFS measures the endogenous la-ser induced tissue fluorescence and, usinga photon migration model, corrects the fluo-rescence lineshape for distortions inducedby tissue scattering and absorption prop-erties.[6] Subsequently, the relative con-centrations of NADH and Collagen are ex-tracted. LSS analyzes the small portion oflight (3-5%) which is singly scattering pri-marily from the epithelial nuclei. Analysisof this singly scattering light provides thesize distribution of epithelial nuclei,[7] aknown hallmark of epithelial dysplasia, acondition in which the likelihood of the tis-sue undergoing malignant change is greatlyincreased. Eighty patients with Barrett’s esophagusunderwent random 4-quadrant biopsiesand optical classification. A consensus di-agnosis of at least 2 expert GI pathologist

classified each site as non-dysplasticBarrett’s (NDB), low-grade dysplasia(LGD), or high-grade dysplasia (HGD). Theconsensus histological diagnosis was lowgrade dysplasia in 23, high grade dysplasiain 15 and non-dysplasia in all other biop-sies. Immediadely prior to biopsy, an opti-cal fiber probe was brought in gentle con-tact with the site and sampled in less than 3s for TMS parameters. Figure 1 illustrates selected tissue param-eters from each spectral modality. The re-duced scattering coefficient decreases forHGD lesions. IFS demonstrates that the ra-tio of NADH to collagen increases system-atically with the progression of dysplasia.Finally, LSS shows an increase in the nuclearenlargement (i.e. percent of nuclei above10µm) for HGD lesions. A diagnostic algo-rithm (using logistic regression) incorpo-

Figure 1. TMS tissue parameters extracted from (a) DRS, (b) IFS, and (c) LSS. Error barsrepresent 95% confidence intervals. Brackets indicate significant correlations.

0.8

1.3

1.8

2.3

2.8

3.3

HGD LGD NDB

µs'(λ

= 63

0 nm

) [m

m-1]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

HGD LGD NDB

NADH/C

ollage

n

0

10

20

30

40

50

60

HGD LGD NDB

Nuc

lear

Enlar

gemen

t [%]

TMS,continues on page 14

Page 14

rating each of these parameters demon-strates the high accuracy of this techniquefor distinguishing HGD from all other sites(sensitivity and specifity >85%). All ofthese algorithms were implemented in cus-tom software (Fig. 2), developed using Na-tional Instruments LabView and MathworksMatlab. Analysis of the entire data set wasautomated and required an average of 0.8 +0.3 s per patient. Real time spectral diagnosis of diseaseoffers exciting new opportunities to aid inthe management of disease detection. Wehave demonstrated for the first time a sys-

Figure 2. Front panel of custom software designed for automated real-time diagnosis of dysplasia using tri-modal spectroscopy.

tem capable of real time detection/analysisof HGD dysplasia in patients with BE. Realtime optical detection/analysis of HGD inBarrett’s esophagus using trimodal spec-troscopy has the potential to guide biopsyand avoid unnecessary biopsy. Future stud-ies aim to show that real-time guide to bi-opsy can enhance the detection of precancerbeyond current clinical practice.

TMS, continued from page 13

References

1. Georgakoudi, I., Sheets, E E., Muller,M. G. et al., Am J Obstet Gynecol 186, 374-82, (2002).

2. I. Georgakoudi, B. C. Jacobson, , J. VanDam, et al., Gastroenterology 120, 1620-9(2001).3. Muller, M. G. , Valdez,T. A., Georgakoudi,I.et al., Cancer 97, 1681-92 (2003).4. Tunnell, J. W., Desjardins, A. E., Galindo,L. et al., Technol Cancer Res Treat 2, 505-14(2003).5. Zonios, G. Perelman, L. T., Backman, V.M. et al., Applied Optics 38, 6628-6637(1999).6. Q. G. Zhang, M. G. Muller, J. Wu, et al.,Optics Letters 25, 1451-1453 (2000).7. Perelman, L. T., Backman, V. M. Wallace,et al., Physical Review Letters 80, 627-630(1998).

Page 15

Recent Spectroscopy Laboratory Published ArticlesAhn, A., Yang, C., Wax, A., Popescu, G.,Fang-Yen, C., Badizadegan, K., Dasari,R.R., and Feld, M.S., “Harmonic Phase Dis-persion Microscope with a Mach-ZenderInterferometer”, Applied Optics 44 (7),1188-1190 (2005).

Chan, Y., Caruge, J.M., Snee, P.T. andBawendi, M.G., “Multiexcitonic Two-StateLasing in a CdSe Nanocrystal Laser”,Appl. Phys. Lett. 85, 2460-2462 (2004).

Chan, Y.T., Zimmer, J.P., Stroh, M., Steckel,J., Jain, R.K. and Bawendi, M.G., “Incor-poration of Luminescent Nanocrystalsinto Monodisperse Core-Shell SilicaMicrospheres”, Adv. Mat. 16, 2093-2097(2004).

Chang, M.C.Y., Yee, C.S., Stubbe, J. andNocera, D.G., “Turning On RibonucleotideReductase by Light-Initiated Amino AcidRadical Generation”, DG. Proc. Natl. Acad.Sci. U.S.A. 101. 6882-7 (2004).

Chang, C.J., Chang M.C.Y., Damrauer N.H.and Nocera D.G., “Proton-Coupled Elec-tron Transfer. A Unifying Mechanism forBiological Charge Transport, Amino AcidRadical Initiation and Propagation, andBond Making/Breaking Reactions of Wa-ter and Oxygen”, Biophys. Biochim. Acta1655, 13-28 (2004).

Cho, S.H., Ram, R.J., Byun, D.S. and Thom,R.L. “Pulsed Light Absorption InducedQuantum Well Intermixing on InGaAsP/InGaAsP MQW Using 532 nm Irradiation”,Trends in Optics and Photonics Series,Conference on Lasers and Electro-Optics,(Optical Society of America) 98/B, CThF5/1-2 (2004).

Clapp, R., Medintz, I.R., Mauro, J.M.,Fisher, B.R., Bawendi, M.G. and Mattoussi,H., “Fluorescence Resonance EnergyTransfer Between Quantum Dot Donorsand Dye Labeled Protein Acceptors”, J.Am. Chem. Soc. 126, 301-310 (2004).

Clauson, S.L., Christensen, S.D. and Spen-cer, K.M., “High Resolution UV EchelleSpectrograph for Environmental Sensing”,SPIE 5269, 34-41 (2004).

Chung I. and Bawendi, M.G., “Relation-ship Between Single Quantum-dot Inter-mittency and Fluorescence Intensity De-cays from Collections of Dots”, Phys. Rev.B 70, 165304 (2004).

Damrauer, N.H., Hodgkiss, J., Rosenthal,J. and Nocera DG. “Observation of Pro-

ton-Coupled Electron Transfer by TransientAbsorption Spectroscopy in a Hydrogen-Bonded, Porphyrin Donor-Acceptor Assem-bly”, J. Phys. Chem. B 108, 6315-21 (2004).

Fecko, C.J., Loparo, J.J. and Tokmakoff, A.,“Generation of 45 Femtosecond Pulses at 3µm with a KNbO3 Optical Parametric Ampli-fier”, Optics Communications 241, 521(2004).

Fisher, B., Eisler, H.-J., Stott, N.E. andBawendi, M.G., “Emission Intensity Depen-dence and Single-Exponential Behavior inSingle Colloidal Quantum Dot FluorescenceLifetimes”, J. Phys. Chem. B 204, 143-148(2004).

Georgakoudi, I. and Feld, M.S., “The Com-bined Use of Fluorescence, Reflectance,and Light-Scattering for Evaluating Dyspla-sia in Barrett’s Esophagus”,. Gastrointesti-nal Endoscopy Clinics of North America 14,519-537 (2004).

Glorieux, C., Beers, J.D., Bentefour, E.H., Vande Rostyne, K. and Nelson, K.A., “PhaseMask-based Interferometer: Operation Prin-ciple, Performance, and Application toThermoelastic Phenomena”, Rev. Sci. Instr.75, 2906-2920 (2004).

Gray, T.G., Veige, A.S. and Nocera, D.G. “Co-operative Bimetallic Reactivity: HydrogenActivation in Two-Electron Mixed-ValenceCompounds”, J. Am. Chem. Soc. 126, 9760-8 (2004).

Gray, T.G., Rudzinski, C.M., Meyer, E.E. andNocera, D.G. “Excited-State Distortion ofRhenium(III) Sulfide and Selenide Clusters”,J. Phys. Chem. A 108, 3238-43 (2004).

Iwai, H., Fang-Yen, C., Popescu, G., Wax, A.,Badizadegan, K., Dasari, R.R. and Feld,M.S., “Quantitative Phase Imaging UsingActively Stabilized Phase Shifting Low-Coherence Interferometry “, Optics Letters29 (20), 2399-2401 (2004).

Jarosz, M.V., Porter, V.J., Fisher, B.R.,Kastner, M.A., Bawendi, M.G., “Photocon-ductivity Studies of Treated CdSe Quan-tum Dot Films Exhibiting Increased ExcitonIonization Efficiency, Phys. Rev. B 70,195327 (2004).

Kay, J.J., Byun, D.S., Clevenger, J.O., Jiang,X., Petrovi´c, V.S., Seiler, R., Barchi, J.R.,Merer, A.J., and Field, R.W., “Spectrum-Only’ Assignment of Core-Penetrating andCore-Nonpenetrating Rydberg States of

Calcium Monofluoride,”. Canad. J. Chem.,82, 791-803 (2004).

Khalil, M., Demirdöven, N. and Tokmakoff,A., “Vibrational Coherence Transfer Char-acterized with Fourier-Transform 2D IRSpectroscopy”, J. of Chemical Phys. 121,362 (2004).

Lee, H.L.T., Boccazzi, P., Gorret, N., Ram,R.J., Sinskey, A.J., “In Situ Bioprocess Moni-toring of Escherichia Coli Bioreactionsusing Raman Spectroscopy,” VibrationalSpectroscopy 35, 131-137 (2004).

Lefebvre-Brion, H. and Field, R.W., “TheSpectra and Dynamics of Diatomic Mol-ecules”, (Elsevier, New York, 2004).

Mishra, A.P., Thom, R.L. and Field, R.W.,“New S1 State Vibrational and T3,2,1 Spin-Rotational Assignments in the Vicinity ofthe A1Au−X1Σ+

g V30K

10 Band”, J. Mol.

Spectrosc. 228, 565-579 (2004).

Nelson, W.H., Dasari, R.R., Feld, MS, andSperry, J.F., “Intensities of CalciumDipicolinate and Bacillus subtilis SporeRaman Spectra Excited with 244 nm Light”,Applied Spectroscopy 58 (12), 1408-1412(2004).

Pistorio, B.J. and Nocera, D.G., “Photochem-istry of Group IV Porphyrin Halides”, J.Photochem. Photobiol. A 162, 563-7 (2004).

Sundar, V.C., Eisler, H.-J., Deng, T., Chan, Y.,Thomas, E.L. and Bawendi, M.G., “Soft-lithographically-Embossed Multi-LayeredDistributed Feedback Nanocrystal Lasers”,Adv. Mat. 16, 2137-2141 (2004).

Taylor, J.W., Ehlker, G., Carstensen, H.-H.,Ruslen, L., Field, R.W. and Green, W.H.,“Direct Measurement of the Fast Revers-ible Addition of Oxygen to CyclohexadienylRadicals in Nonpolar Solvents”, Journal ofPhysical Chemistry A 108 (35), 7193-7203(2004).

Souza Filho, A.G., Chou, S.G., Samsonidze,G.G., Dresselhaus, G., Dresselhaus, M.S., An,L., Liu, J., Swan, A.K., Ünlü, M.S., Goldberg,B.B., Jorio, A., Gruneis, A. and Saito, R.,“Stokes and Anti-Stokes Raman Spectra ofSmall Diameter Isolated CarbonNanotubes”, Phys. Rev. B 69, 115428 (2004).

Walker, G.W. and Nocera, D.G., “[Ru(4,7-diphenyl-1,10-phenanthroline)3]Cl2”, Inorg.Synth. 34, 66-8 (2004).

MASSACHUSETTS INSTITUTE OF TECHNOLOGYG. R. HARRISON SPECTROSCOPY LABORATORYCAMBRIDGE, MA 02139-4307

Nonprofit OrganizationUS PostagePAIDCambridge, MAPermit No. 54016

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