UV absorption spectra of HO 2 , CH 3 O 2 , C 2 H 5 O 2 , and CH 3 C(O)CH 2 O 2 radicals and mechanism of the reactions of F and Cl atoms with CH 3 C(O)CH 3

Pulse radiolysis techniques were used to measure the gas phase UV absorption spectra of the title peroxy radicals over the range 215–340 nm. By scaling to σ(CH 3 O 2 ) 240 nm = (4.24 ± 0.27) × 10 −18 , the following absorption cross sections were determined: σ(HO 2 ) 240 nm = 1.29 ± 0.16, σ(C 2 H 5 O 2 ) 240 nm = 4.71 ± 0.45, σ(CH 3 C(O)CH 2 O 2 ) 240 nm = 2.03 ± 0.22, σ(CH 3 C(O)CH 2 O 2 ) 230 nm = 2.94 ± 0.29, and σ(CH 3 C(O)CH 2 O 2 ) 310 nm = 1.31 ± 0.15 (base e, units of 10 −18 cm 2 molecule −1 ). To support the UV measurements, FTIR‐smog chamber techniques were employed to investigate the reaction of F and Cl atoms with acetone. The F atom reaction proceeds via two channels: the major channel (92% ± 3%) gives CH 3 C(O)CH 2 radicals and HF, while the minor channel (8% ± 1%) gives CH 3 radicals and CH 3 C(O)F. The majority (>97%) of the Cl atom reaction proceeds via H atom abstraction to give CH 3 C(O)CH 2 radicals. The results are discussed with respect to the literature data concerning the UV absorption spectra of CH 3 C(O)CH 2 O 2 and other peroxy radicals. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 283–291, 2002