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

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

CH 3 I or CH 3 C(O)CH 3 sample in sample out Flow Controller O2O2 T0T0 A B C D DG535 PC pump TA reactor / White cell Excimer Laser 193 nm CH 3 C(O)CH nm CH 3 I 1 D.-R. Huang, L.-K. Chu, and Y.-P. Lee, J. Chem. Phys. A 127, (2007)

ν 1 (a’)ν 2 (a’)ν 9 (a”)Reference Ar matrix2968 a Ase [2] Ar matrix Nandi [3] He nanodroplet Morrison [4] Time-resolved FTIR Huang [1] Time-resolved FTIR This work a Originally assigned to ν 9 1 D.-R. Huang, L.-K. Chu, and Y.-P. Lee, J. Chem. Phys. A 127, (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)

Parameters (cm -1 ) A’’1.730 B’’0.379 C’’0.330 A’1.726 B’0.379 C’0.330 a:b:c0.76:0.24:0 T = 300K B3LYP/aug-cc-pVTZ

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

A R ’’ a B R ’’ a C R ’’ a D R ’’a F·a 1 ’’ AR’AR’ a BR’BR’ a CR’CR’ a DR’DR’ a a F·a 1 ’ a:b:c a 0.86:0.14:0 a Effective parameters from the asymmetric rotor model simulation b G. M. P. Just, A. B. McCoy, T. A. Miller J. Chem. Phys. 127, (2007)

A R ’’ a B R ’’ a C R ’’ a D R ’’a F·a 1 ’’ b 1.64 AR’AR’ a BR’BR’ a CR’CR’ a DR’DR’ a a F·a 1 ’ a:b:c a 0.86:0.14:0 a Effective parameters from the asymmetric rotor model simulation b G. M. P. Just, A. B. McCoy, T. A. Miller J. Chem. Phys. 127, (2007)

A R ’’ a B R ’’ a C R ’’ a D R ’’a F·a 1 ’’ b AR’AR’ a BR’BR’ a CR’CR’ a DR’DR’ a a F·a 1 ’ a:b:c a 0.86:0.14:0 a Effective parameters from the asymmetric rotor model simulation b G. M. P. Just, A. B. McCoy, T. A. Miller J. Chem. Phys. 127, (2007)

A R ’’ a B R ’’ a C R ’’ a D R ’’a Fa1’’ b b 1.64 AR’AR’ a BR’BR’ a CR’CR’ a DR’DR’ a Fa1’ Shift0-0.3 Boltzmann Factor 1 b 0.55 a a:b:c a 0.86:0.14:0 a Effective parameters from the asymmetric rotor model simulation b G. M. P. Just, A. B. McCoy, T. A. Miller J. Chem. Phys. 127, (2007)

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

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

Parameters (cm -1 ) for origin Parameters (cm -1 ) for A R ’’ B R ’’ C R ’’ D R ’’ Fa1’’ AR’AR’ BR’BR’ CR’CR’ DR’DR’ Fa1’00 Shift00 Boltzma nn Factor a:b:c0.86:0.14:0