Time-resolved laser magnetic resonance study of deactivation of Cl(P-2(1/2))

Rate constants for the collisional deactivation of spin-orbitally excited C l* (equivalent to Cl(P-2(1/2))) atoms by some selected gases have been dete rmined using time-resolved laser magnetic resonance (LMR) techniques. Cl* a toms were produced by photodissociation of ICl at 248 nm, and the relative quantum yield of Cl* atoms is determined to be 0.47 +/- 0.06. The rate cons tants for the relaxation of Cl* (x10(-11) cm(3)/molecule.s, +/- 2 sigma) by H-2(5.5 +/- 1.6), HF(1.4 +/- 0.4), DF(0.7 +/- 0.2), DCl(0.7 +/- 0.2), HBr( 1.2 +/- 0.36), DBr(1.4 +/- 0.4), NO(0.66 +/- 0.2), SO2 (1.9 +/- 0.5), N2O ( 0.63 +/- 0.2), NF3 (22 +/- 6), CH4 (1.9 +/- 0.6), CD4 (13 +/- 4), CF4 (2.4 +/- 0.7), SiF4 (14 +/- 4), and SF6 (18 +/- 5) at 298 K are reported. The ra te constants of the reactions of ground state Cl(P-2(3/2)) atoms with HBr a nd DBr were found to be, in units of x10(-11) cm(3)/molecule.s, 0.75 +/- 0. 15 and 0.50 +/- 0.10, respectively. The study of the deactivation process I (P-2(1/2))+ICl --> Cl-*+I-2 (a), Cl+I-2 (b), I+ICl (c) yielded the ratios k (a)/(k(a)+k(b))=0.63 +/- 0.17, k(a)/(k(a)+k(b)+k(c))greater than or equal t o 0.70. (C) 2000 American Institute of Physics. [S0021-9606(00)01406-9].