Chirped Pulse Microwave Spectroscopy on Methyl Butanoate Alicia

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Chirped Pulse Microwave Spectroscopy on Methyl Butanoate Alicia Hernandez-Castillo, Brian Hays, Chamara Abeysekara, and

Chirped Pulse Microwave Spectroscopy on Methyl Butanoate Alicia Hernandez-Castillo, Brian Hays, Chamara Abeysekara, and Timothy Zwier

Motivation • Methyl Butanoate has the major groups to compare to biofuels • The

Motivation • Methyl Butanoate has the major groups to compare to biofuels • The decomposition products can proceed through several channels • The oxidative chemistry has been modelled before

Theory • Conformational search performed with the MM 2* force field using Macro. Model

Theory • Conformational search performed with the MM 2* force field using Macro. Model • Optimized structures at the MP 2/aug-cc-p. VTZ level of theory using Guassian 09 with ZPVE pt gg tt tg

Experimental Guzik 40 GS/s digitizer 13 GHz bandwidth

Experimental Guzik 40 GS/s digitizer 13 GHz bandwidth

Experimental

Experimental

Spectrum 1. 5 million averages 25 averages/gas pulse 10% TWTA Gain 15 PSI He

Spectrum 1. 5 million averages 25 averages/gas pulse 10% TWTA Gain 15 PSI He

Conformation-Specific Spectroscopy • The initial analysis was done using Strong Field Coherence Breaking technique

Conformation-Specific Spectroscopy • The initial analysis was done using Strong Field Coherence Breaking technique to find which transitions belonged to which conformer • Will be discussed in full detail in tomorrow’s talks

Conformation-Specific Spectroscopy • The initial analysis was done using Strong Field Coherence Breaking TG

Conformation-Specific Spectroscopy • The initial analysis was done using Strong Field Coherence Breaking TG 03 and TG 04 in the technique to find which transitions Spectroscopy in Atmospheric belonged to which Chemistry Mini-Symposium conformer Tuesday afternoon • Will be discussed in full detail in tomorrow’s talks

Spectrum

Spectrum

Tunneling Splitting Fit using the XIAM program C. C. Lin and J. D. Swalen,

Tunneling Splitting Fit using the XIAM program C. C. Lin and J. D. Swalen, Rev. Mod. Phys. 31, 841 -892 (1959) H. Hartwig and H. Dreizler, Z. Naturforsch 51 a, 923 -932 (1996)

Methyl rotor Tunneling Splitting E A E Conformer tt E A Conformer tg A

Methyl rotor Tunneling Splitting E A E Conformer tt E A Conformer tg A * A

Methyl rotor Tunneling Splitting E A E Conformer tt E A Conformer tg A

Methyl rotor Tunneling Splitting E A E Conformer tt E A Conformer tg A * A

Methyl rotor Tunneling Splitting E A E E&A Conformer tt E A E A

Methyl rotor Tunneling Splitting E A E E&A Conformer tt E A E A E Conformer 2 A * A

Internal Rotor Fit Experimental Theoretical A (MHz) 8349. 7639(25) 8377. 873 B (MHz) 1197.

Internal Rotor Fit Experimental Theoretical A (MHz) 8349. 7639(25) 8377. 873 B (MHz) 1197. 763(13) 1206. 8277 C (MHz) 1076. 547(91) 1082. 9548 DJ (k. Hz) 0. 052(20) DJK (k. Hz) 0. 039784 d. J (k. Hz) 0. 0117(24) V 3 (cm-1) 395(24) F 0 (GHz) 150. 3(8. 0) epsilon (rad) -2. 67 (20) delta (rad) 0. 468(85) N 32 rms (MHz) 0. 040843 Jmax 12 tt conformer

Internal Rotor Fit A (MHz) B (MHz) C (MHz) DJ (k. Hz) DJK (k.

Internal Rotor Fit A (MHz) B (MHz) C (MHz) DJ (k. Hz) DJK (k. Hz) DK (k. Hz) d. J (k. Hz) V 3 (cm-1) F 0 (GHz) epsilon (rad) delta (rad) N rms (MHz) Jmax Experimental 6059. 353(17) 1421. 3492(24) 1333. 3682(28) 0. 477(38) -6. 03(26) 51. 5(2. 3) -0. 083(29) 426(16) 160. 8(5. 3) -6. 02(32) 0. 5404(49) 47 0. 029952 7 Theoretical 5828. 7687 1450. 984 1379. 7689 tg conformer

Conformers Found • No Conformer gg or pt found • No evidence for more

Conformers Found • No Conformer gg or pt found • No evidence for more conformers pt gg tt tg

Conformers Found • No Conformer gg or pt found • No evidence for more

Conformers Found • No Conformer gg or pt found • No evidence for more conformers Conformational Cooling pt gg tt tg

Relative Populations • Using rotation diagram method with the form: J. M. Oldham, C.

Relative Populations • Using rotation diagram method with the form: J. M. Oldham, C. Abeysekara, et al. J. Chem. Phys. 141, 154202 (2014)

Relative Populations tt 40% tg 60%

Relative Populations tt 40% tg 60%

Future Work • Are more conformers available in the jet cooled spectrum • Look

Future Work • Are more conformers available in the jet cooled spectrum • Look for more conformers and excited vibrational states in room temperature cell • Pyrolysis on methyl butanoate to look for radicals such as:

Acknowledgements The Zwier Group #55152 -ND 6

Acknowledgements The Zwier Group #55152 -ND 6