1. 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

2. Motivation 2 Titan is a model system for studies of primordial Earth 2 Titan’s 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 Titan’s atmosphere.

3. Gas phase, jet-cooled vibronic spectroscopy study of the phenylcyanomethyl radical (PCM). Doubly resonance stabilized Motivation 3 PCM

4. Motivation 4 A comparison to the vibronic spectroscopy of 1- phenylpropargyl radical (1PPR) will be presented. PCM1PPR

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)

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

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

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

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

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”

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

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.

13. 13 Origin 201cm -1 Lifetime of Select Bands (at threshold IP) ∆ t (ns) Ion Signal 050010001500

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

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 hνhν dischargebenzylisocyanide benzylcyanide

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)