KuoHsiang Hsu and YuanPern Lee Department of Applied

Kuo-Hsiang Hsu and Yuan-Pern Lee Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Taiwan Meng Huang and Terry A. Miller Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University

Introduction CH 3 OO Radical In combustion and atmospheric chemistry, alkyl peroxy radicals are important intermediates Oxidation of NO to NO 2 (Formation of Ozone) Formation of acid rain Reaction intermediate of fossil fuels combustion Methyl peroxy is the simplest alkyl peroxy radical The methyl group torsion in methyl peroxy provides good system for studying the effect of large amplitude motion

[1] FTIR Experimental Apparatus DG 535 T 0 A B C D Flow Controller PC O 2 CH 3 I or CH 3 C(O)CH 3 reactor / White cell sample in TA sample out pump Excimer Laser 193 nm CH 3 C(O)CH 3 248 nm CH 3 I 1 D. -R. Huang, L. -K. Chu, and Y. -P. Lee, J. Chem. Phys. A 127, 234318 (2007)

Experimental Result

Experimental Result ν 1 (a’) ν 2 (a’) ν 9 (a”) Reference 2968 a 2954 2955. 5 3024. 5 Ase[2] Nandi[3] Morrison[4] Ar matrix He nanodroplet 3032 3034. 7 Time-resolved FTIR 3033 2954 3020 Huang[1] Time-resolved FTIR 3032. 3 2954. 3 3021. 4 This work a. Originally assigned to ν 9 Huang, L. -K. Chu, and Y. -P. Lee, J. Chem. Phys. A 127, 234318 (2007) 2 P. Ase, W. Bock, and A. Snelson, J. Phys. Chem. 90, 2099 (1986) 3 Nandi et al. , J. Phys. Chem. A 106, 7547 (2001) 4 Morrison et al. J. Phys. Chem. A 116, 5299 (2012) 1 D. -R.

Experimental Result - �� 2

Simulation of �� 2 Band Parameters (cm-1) A’’ 1. 730 B’’ 0. 379 C’’ 0. 330 A’ 1. 726 B’ 0. 379 C’ 0. 330 a: b: c 0. 76: 0. 24: 0 T = 300 K B 3 LYP/aug-cc-p. VTZ

Broadening in Q-Branch Torsional Sequence Bands -1[5] �� =125 cm 12 Tunneling splitting in torsional eigenvalues The torsion- rotation coupling will affect the pattern of the spectrum 5 G. M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007)

Model for Simulation of Torsional Sequence Band 5 G. M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007)

Model for Simulation of Torsional Sequence Band

AR’’ a 1. 7063 BR’’ a 0. 4026 CR’’ a 0. 3300 DR’’ a-0. 1768 F·a 1’’ AR’ a 1. 7023 BR’ a 0. 4026 CR’ a 0. 3300 DR’ a-0. 1768 a 0. 307 a. Effective parameters from the asymmetric rotor model simulation b. G. M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007) F·a 1’ a: b: c a 0. 86: 0. 14: 0

AR’’ a 1. 7063 BR’’ a 0. 4026 CR’’ a 0. 3300 DR’’ a-0. 1768 F·a 1’’ b 1. 64 AR’ a 1. 7023 BR’ a 0. 4026 CR’ a 0. 3300 DR’ a-0. 1768 a 0. 307 F·a 1’ a. Effective b. G. parameters from the asymmetric rotor model simulation M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007) a: b: c a 0. 86: 0. 14: 0

AR’’ a 1. 7063 BR’’ a 0. 4026 CR’’ a 0. 3300 DR’’ a-0. 1768 F·a 1’’ b-12. 60 AR’ a 1. 7023 BR’ a 0. 4026 CR’ a 0. 3300 DR’ a-0. 1768 a 0. 307 F·a 1’ a. Effective b. G. parameters from the asymmetric rotor model simulation M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007) a: b: c a 0. 86: 0. 14: 0

Simulation of �� 2 with Torsional Sequence Band AR’’ a 1. 7063 BR’’ a 0. 4026 CR’’ a 0. 3300 DR’’ a-0. 1768 Fa 1’’ b-0. 06 b 1. 64 AR’ a 1. 7023 BR’ a 0. 4026 CR’ a 0. 3300 DR’ a-0. 1768 Shift 0 -0. 3 Boltzmann Factor 1 b 0. 55 Fa 1’ a 0. 307 a. Effective parameters from the asymmetric rotor model simulation b. G. M. P. Just, A. B. Mc. Coy, T. A. Miller J. Chem. Phys. 127, 044310 (2007) a: b: c a 0. 86: 0. 14: 0

Summary FTIR spectrum of CH 3 OO in MIR range has been measured in this work R = 0. 15 cm-1 ν 1 , ν 2 , ν 9 transitions are assigned, which have good agreement with previous work Good simulation of rotation structure has been obtained in ν 2 band, especially in P and R-branch The rotational structure of Q-branch ν 2 can be simulated by considering torsion-rotation coupling The decrease of tunneling splitting in the vibrational excited state may be caused by couplings between vibrational modes

Acknowledgement Prof. Terry A. Miller Prof. Anne B. Mc. Coy Dr. Mourad Roudjane Dr. Dmitry Melnik Terrance J. Codd Rabi Chhantyal-Pun Neal D. Kline Thank You!