Excited Cl((2)P(1/2)) atoms: yield from the photodissociation of SOCl(2) and collisional deactivation by NO(2), CCl(3)H, C(2)H(4), C(3)H(6), and SOCl(2).

Rate constants for the collisional deactivation of spin-orbitally excited Cl* ( identical withCl((2)P(1/2))) atoms by some selected gases at T = 298 K have been determined using time-resolved laser magnetic resonance (LMR) techniques. Cl* atoms were produced by photodissociation of SOCl(2) at 248 nm, and the relative quantum yield of Cl* atoms is determined to be 0.52 +/- 0.03. This yield is much larger than the yield at 235 nm (0.35 +/- 0.06). The rate constants for the relaxation of Cl* (x10(-11) cm(3)/s, +/- 2sigma) by NO(2)(1.5 +/- 0.4), C(2)H(4) (18 +/- 5), CCl(3)H (1.8 +/- 0.4), CH(3)-CH=CH(2) (16 +/- 4), and SOCl(2) (0.62 +/- 0.2) are reported for the first time. All of them are pressure-independent, and in all cases the dominant channel is physical quenching. It was established that the spin-orbital excitation of chlorine atoms decreases the probability of chemical reactions in collisions with propylene molecules. The rate constants of the reactions of ground state Cl((2)P(3/2)) atoms with C(2)H(4), CH(3)-CH=CH(2), and SOCl(2) at T = 298 K were found to be (5.0 +/- 1) x 10(-30) cm(6)/s (P(Ar) = 8-15 Torr), (5.2 +/- 1) x 10(-11) cm(3)/s (P(Ar) = 9-12 Torr), and (6 +/- 4) x 10(-14) cm(3)/s, respectively; the first one is termolecular, the last two are bimolecular, and the buffer gas is Ar.