VIBRONIC SPECTROSCOPY OF THE PHENYLCYANOMETHYL RADICAL 6/23/11 1 DEEPALI N. MEHTA, NATHANAEL M....
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VIBRONIC SPECTROSCOPY OF THE PHENYLCYANOMETHYL RADICAL 6/23/11 1 DEEPALI N. MEHTA, NATHANAEL M. KIDWELL, JOSEPH A. KORN, AND TIMOTHY S. ZWIER 66 th International
VIBRONIC SPECTROSCOPY OF THE PHENYLCYANOMETHYL RADICAL 6/23/11
1 DEEPALI N. MEHTA, NATHANAEL M. KIDWELL, JOSEPH A. KORN, AND
TIMOTHY S. ZWIER 66 th International Symposium on Molecular
Spectroscopy RJ04 Department of Chemistry, Purdue University West
Lafayette, IN 47907
Slide 2
Motivation 2 Titan is a model system for studies of primordial
Earth 2 Titans chemistry occurs via ion and neutral pathways 2
Resonance stabilized radicals (RSRs) are thought to be key
intermediates in the formation of larger molecules 3 long lifetimes
build up in concentration Nitrile and isonitrile RSRs could be
especially important in the chemistry of Titan complex
nitrogen-containing compounds aerosols (tholins) [1] Kemsley,
J.,Chemical and Engineering News, 2007, 85, 11, Science, 2007, 316,
870-875 [2] Raulin, F., Space Sci. Rev. 135, 2008, 37-48 [3]Neil J.
Reilly; Damian L. Kokkin; Masakazu Nakajima; Klaas Nauta; Scott H.
Kable; Timothy W. Schmidt; J. Am. Chem. Soc. 2008, 130, 3137-3142.
Figure 1 1 : Schematic of reactions in Titans atmosphere.
Slide 3
Gas phase, jet-cooled vibronic spectroscopy study of the
phenylcyanomethyl radical (PCM). Doubly resonance stabilized
Motivation 3 PCM
Slide 4
Motivation 4 A comparison to the vibronic spectroscopy of 1-
phenylpropargyl radical (1PPR) will be presented. PCM1PPR
Slide 5
Experimental 5 EXCITE Collisional cooling to zero- point
vibrational levels Precursor sample D0D0 Cooling Supersonic
Expansion benzyl cyanide phenylcyanomethyl radical Discharge Source
Valve Face Ceramic Spacer Delrin Insulator Delrin Cap Electrode
(-150V) Electrode (+550V)
Slide 6
Experimental 6 Laser Ports 2 Stage Ion Acceleration Einzel Lens
Pulsed Valve MCP Time-of-Flight Tube Turning Prism Mass Gate Pulser
Discharge Source 1C-R2PI Ionization continuum SnSn S0S0 2C-R2PI
DnDn D0D0 Tuned Laser Method of Detection: Resonant 2 Photon
Ionization (R2PI) followed by detection with a Time of Flight (TOF)
mass spectrometer Tuned Laser Fixed Laser
Slide 7
2C-R2PI Phenylcyanomethyl (PCM) Radical (with tentative
assignments) 7 a Time Dependent Density Functional Theory (DFT):
B3LYP/6-311+G(d,p). Origin at 21,402cm -1. D 1 ( 2 A) D 0 ( 2 A)
transition a 000000
Slide 8
2C-R2PI Comparison for PCM and 1PPR 8 Special thanks to the
Timothy Schmidt group for providing the 1PPR excitation spectrum
file! [3] Neil J. Reilly; Damian L. Kokkin; Masakazu Nakajima;
Klaas Nauta; Scott H. Kable; Timothy W. Schmidt; J. Am. Chem. Soc.
2008, 130, 3137-3142. [4] Neil J. Reilly; Masakazu Nakajima, Bligh
A. Gibson, Timothy W. Schmidt, and Scott H. Kable; J. Chem. Phys,
2009, 130, 144313 PCM 1PPR
Slide 9
2C-R2PI Comparison for PCM and 1PPR 9 PCM 1PPR Special thanks
to the Timothy Schmidt group for providing the 1PPR excitation
spectrum file! [3] Neil J. Reilly; Damian L. Kokkin; Masakazu
Nakajima; Klaas Nauta; Scott H. Kable; Timothy W. Schmidt; J. Am.
Chem. Soc. 2008, 130, 3137-3142. [4] Neil J. Reilly; Masakazu
Nakajima, Bligh A. Gibson, Timothy W. Schmidt, and Scott H. Kable;
J. Chem. Phys, 2009, 130, 144313
Slide 10
Comparison of PCM and 1PPR Normal Modes 10 Comparison of Normal
Modes in PCM and 1PPR PCM1PPR 3,4 Normal Mode Experimental (cm -1 )
Calculated a (cm -1 ) Normal Mode Experimental (cm -1 )
2194390022915 2278975423768 2541340327422 2711611329117 a Ground
state frequencies were calculated using Density Functional Theory
(DFT): B3LYP/6-311+G(d,p). Calculated frequencies were scaled by
0.90 to approximate the excited state geometry change. PCM 27 25 22
21 22 23 27 29 1PPR [3] Neil J. Reilly; Damian L. Kokkin; Masakazu
Nakajima; Klaas Nauta; Scott H. Kable; Timothy W. Schmidt; J. Am.
Chem. Soc. 2008, 130, 3137-3142. [4] Neil J. Reilly; Masakazu
Nakajima, Bligh A. Gibson, Timothy W. Schmidt, and Scott H. Kable;
J. Chem. Phys, 2009, 130, 144313 12 6b 6a
Slide 11
Rotational Band Contours of Select Bands 11 201cm -1 Origin
2C-R2PI over vibronic band of interest Resolution is 0.08cm -1 c a
b
Slide 12
Ionization Potential of Select Bands for PCM 12 D0D0 D1D1 Ion +
e - Tuned Laser 201cm -1 Origin IP=7.935eV 1PPR IP=7.3eV 3 Fixed
Laser [3] Neil J. Reilly; Damian L. Kokkin; Masakazu Nakajima;
Klaas Nauta; Scott H. Kable; Timothy W. Schmidt; J. Am. Chem. Soc.
2008, 130, 3137-3142.
Slide 13
13 Origin 201cm -1 Lifetime of Select Bands (at threshold IP) t
(ns) Ion Signal 050010001500
Slide 14
Summary 14 [3] Neil J. Reilly; Damian L. Kokkin; Masakazu
Nakajima; Klaas Nauta; Scott H. Kable; Timothy W. Schmidt; J. Am.
Chem. Soc. 2008, 130, 3137-3142. [4] Neil J. Reilly; Masakazu
Nakajima, Bligh A. Gibson, Timothy W. Schmidt, and Scott H. Kable;
J. Chem. Phys, 2009, 130, 144313 PCM 1PPR PCM and 1PPR Comparison
PropertyPCM1PPR 3,4 D 0 -D 1 origin (cm -1 )21,40221,007 Lifetime
(ns) 455 61350 Ionization Potential (eV) 7.9357.3
Slide 15
Future Directions 15 Obtain Dispersed Fluorescence (DFL)
spectra for PCM Pursue study of the phenylisocyanomethyl (PICM)
radical Excitation Spectrum Lifetime Ionization Potential Resonant
Ion Dip Infrared Spectroscopy PICM hh dischargebenzylisocyanide
benzylcyanide
Slide 16
Acknowledgements 16 Professor Timothy S. Zwier The Zwier Group
Josh Sebree (TB08, TD11) Evan Buchanan (WI10) Zachary Davis James
Redwine Jacob Dean (RG11) Nathanael Kidwell (WI11) Joseph Korn Di
Zhang Professor Timothy W. Schmidt (The University of Sydney)