The gas-phase depletion kinetics of Cr(a(7)S(3), a(5)S(2), a(5)D(J)) in the
presence of SO2 are reported. Chromium atoms were produced by the 248 nm p
hotodissociation of chromium carbonyl and were detected by laser-induced fl
uorescence. The ground state of Cr, a(7)S(3), was found to react rapidly vi
a a termolecular mechanism with SO2. At 297 K, the limiting low-pressure th
ird-order rate constant is k(o) = (2.68 +/- 0.41) x 10(-28) cm(6) molecule(
-2) s(-1), and the limiting high-pressure second-order rate constant is k(i
nfinity) = (2.73 +/- 0.38) x 10(-10) cm(3) molecule(-1) s(-1); the uncertai
nties represent +/-1 sigma in precision. k(0) was found to decrease with in
creasing temperature. The binding energy of CrSO2 is estimated at 53 kcal m
ol(-1) from combining the kinetic results with unimolecular rate theory and
density functional theory. Cr(a(5)S(2)) depleted with a rate constant of k
= 6.32 x 10(-10) cm(3) molecule(-1) s(-1), and the a(5)D(J) spin/orbit sta
tes depleted at the collision rate of 2.97 x 10(-10) cm(3) molecule(-1) s(-
1); overall uncertainties are estimated at less than or equal to 35%. Both
chemical and physical quenching are likely for the excited states. The pres
ent work completes a study on the depletion kinetics of group 6 transition
metal atoms by SO2. Results are interpreted in terms of long-range attracti
ve forces between Cr and SO2 and the orbital occupancies of the Cr atomic s
tates.