Coherent Synchrotron Radiation for Rotational Spectroscopy : application to

Propynal in the 200-750 GHz rangeJ.Barros P.Roy L.Manceron

SOLEIL - AILES beamline - France D.Apadoo, D. McNaughton E. Robertson

Australian Light source and Monash U.

MSS Columbus 2013

Outline

Introduction1. CSR generation2. Adaptation to AILES beamline3. Noise correction4. Use of CSR for measurements on Propynal

High Resolution IR spectroscopy with Synchrotron Radiation

Introduction

Synchrotron beam

Bruker 125HR Interferometer

resolution: 0.001 cm-1

Bolometer

path difference

14x103

12

10

8

6

4

2

0

Inte

nsité

(u.a

.)

wavenumber

Fourier

Transform

MOPD

8.82 m

Fixed mirror

Moving mirror

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10

Emission modes

depends on sz (electron bunch length) and on the current

1. CSR generation

N≈108 l < sz incoherent emissionEmission mode

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N≈108

10

l < sz incoherent emission

Emission mode

Emission modes

l ≥ sz coherent emission

CSR

depends on sz (electron bunch length) and on the current

1. CSR generation

4

“Clearly the promise of a bright, high-power THz continuum source is attractive. However, we note that CSR is itself a non-linear effect and so may

tend to be inherently noisy.”

R. W. McKellar, J. Mol. Spectrosc. 262, 1 (2010)«High Resolution IR spectroscopy with synchrotron radiation»

CSR instabilities

Microbunching: interaction of an electron bunch with its own emitted radiation

Bunch profile modulation

C. Evain, J. Barros et al., EPL 98, 40006 (2012)

1. CSR generation

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CSR instabilities

Microbunching: interaction of an electron bunch with its own emitted radiation

Bunch profile modulation

C. Evain, J. Barros et al., EPL 98, 40006 (2012)

1. CSR generation

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CSR instabilities

Microbunching: interaction of an electron bunch with its own emitted radiation

Bunch profile modulation

C. Evain, J. Barros et al., EPL 98, 40006 (2012)

1. CSR generation

Fluxscales with NN≈108 l < sz incoherent emission

Emission mode

l ≥ sz coherent emission scales with N²

Microstructures emit coherently

very irregular

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Effect of increasing current

No detected CSR

2. Adaptation to the AILES beamline

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Effect of increasing current

No detected CSR

CSR appearsGain in

intensity: 104 to 105

2. Adaptation to the AILES beamline

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Effect of increasing current

No detected CSR

CSR appearsGain in

intensity: 104 to 105

Microbunching instability

2. Adaptation to the AILES beamline

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Effect of bunch length

Stability zone in bunch length and current

2. Adaptation to the AILES beamline

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Broadband source, but still some remaining noise at given frequenciesEffect of microbunching evidenced even under threshold2

2. Adaptation to the AILES beamline

Signal spectral distribution Noise frequencies

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Noise correction setup

Synchrotron beam

Bruker 125HR Interferometer

Bolometer 1Interferogram

+ perturbation

3. Noise correction

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Noise correction setup

3. Noise correction

Synchrotron beam

Bruker 125HR Interferometer

Bolometer 1Interferogram

+ perturbation

6 µm Mylar beamsplitter

R/T≈0,2

Bolometer 2Perturbation

only

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Noise correction setup

3. Noise correction

4.2 K composite bolometers with identical 0-200 cm-1 filters, same solid angle, same preamplifiersSimultaneous acquisition

Synchrotron beam

Bruker 125HR Interferometer

Bolometer 1Interferogram

+ perturbation

6 µm Mylar beamsplitter

R/T≈0,2

Bolometer 2Perturbation

only

Post-treatment: subtraction of the 2 temporal signals FT

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Correction examples

Periodic perturbationArtifact on an absorbance spectrum compensated

White noise correction

Aperiodic, bursting perturbationTop-up correction: effect on spectrum

3. Noise correction

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Correction examples

3. Noise correction

Example on a 45 min spectrumRes = 0.001 cm-1

Pure rotational line of N2O with an intensity of9.0∙10-23 cm-1/(moleculexcm²) Gain of 5 in S/N

J. Barros and coll. Rev. Sci. Inst. 84, 033102(2013)

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Application

Rotational spectrum of propynal0.225 mbar in 885 cm, 9h, bolometer 4.2 K

About 1200 pure rotational transitions in the ground statePrevious works: Winnewisser, 1972 (90 transitions)McKellar (IR combination differences)

Fit of the ground state (Watson a-type Hamiltonian)

4. Propynal

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Application

Rotational spectrum of propynal0.225 mbar in 885 cm, 9h, bolometer 4.2 K

4. Propynal

14

Application

J=38 → 39 J=39 → 40

not present in the fit

Spectrum

Simulation

4. Propynal

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Some improvements in the molecular constants

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Constants  this work (MHz)   Winnewisser (MHz)  McKellar et al. (MHz)

RotationalABC

 a68035,308 (025)

b4826,28805 (097)4499,52695 (095)

 68035,299 (043)4826,3014 (073)4499,5107 (069)

 68035,263 (039)4826,293 (006)4497,15 (006)

Centrifugal Distorsion QuarticΔJ

ΔJK

ΔK

δJ

δK

   

a1,91792 (111) · 10-3

a-0,1481185 (186)a9,0033 (057)

a3,37419 (151) · 10-4

b0,03396 (026)

   

1,917 (012) · 10-3

-0,148102 (047)8,991240 (9730)3,458 (014) · 10-4

0,019500 (1590)

   

1,913 (004) · 10-3

-0,148044 (039)8,993 (009)

3,454 (012) · 10-4

0,0347 (028)

SexticHJK

HKJ

HK

HJ

 -0,8348 (082) · 10-6

b-8,245 (107) · 10-6

3,190 (147) · 10-3

7,549 (214) · 10-9

 -7,41 (059) · 10-7

-8,310 (130) · 10-6

----

 -7,11 (048) · 10-7

-8,24 (012) · 10-6

2,36 (006) · 10-3

--

Conclusions

Extension of SR spectral range at SOLEIL

BUT Limited Resolution (30MHz..)

- Time-saving for studies of unstable molecules- Combination with IR studies on the same setups- Intensity studies are possible

Frequency

0.1 THz 1 THz 10 THz 100 THz

ISRHigh res.

Wavenumber

3.3 cm-1 33 cm-1 330 cm-1 3300 cm-1

CSRHigh res.

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Two important WEB Pages :

http://www.synchrotron-soleil.fr/

For general informations

http://www.synchrotron-soleil.fr/portal/page/portal/Recherche/LignesLumiere/AILES

and, for proposal submissions :

http://sunset.synchrotron-soleil.fr/sun/

twice a year : mid-september and –february deadlines. Proposals (submissions in English) ranked by an international peer-review committee.

How to submit your proposals

Support from User Office

Preparing your experiment

Safety requirements

Beamline AILES: Mid IR to THz Spectroscopy

Acknowledgements

Lille:Clément EvainSerge BielawskiChristophe Szwaj

SOLEIL- Machine:Marie-Emmanuelle CouprieMarie-Agnès TordeuxPascale BrunelleLaurent NadolskiAlex LoulergueMarie LabatLodovico CassinariRyutaro NagaokaAmor Nadji

MSS Columbus 2013