The gas phase depletion kinetics of Nb(a6D J ,a4F J ) in the presence of O2, SO2, CO2, N2O, and NO are reported. Niobium atoms were produced by the 248 nm photodissociation of Nb(C5H5)(CO)4 and detected by laser-induced fluorescence. The ground term of Nb(4d45s a6D J ) reacts at or above the collision rate with all of the aforementioned oxidants. The first excited term, Nb(4d35s a4F J ), is not as reactive with these oxidants. Results are interpreted in terms of long-range attractions and valence interactions. Additionally, we report reaction rate constants for ground state Nb interacting with N2, CH4, and SF6. Nb(a6D J ) is unreactive toward CH4. Nb(a6D J ) + N2 is pressure dependent at 297 K with k 0 = (2.6 ± 0.3) × 10-32 cm6 s-1 and k ∞ = (4.1 ± 0.5) × 10-13 cm s-1. Nb(a6D J ) + SF6 is temperature dependent with the rate constants given by k(T) = (1.2 ± 0.3) × 10-10 exp[−(4.8 ± 0.2) kcal mol-1/RT] cm3 s-1. Depletion of the aF J term by N2, SF6, and CH4 is J-dependent.

The gas phase collisional disappearance of Mo(a 7 S 3 ,a 5 S 2 ,a 5 D J ) in the presence of N 2 , SO 2 , CO 2 , N 2 O, and NO over the temperature range 294-621 K and in the total pressure range 10-600 Torr is reported. Mo atoms were produced by the 248 nm photodissociation of Mo(CO) 6 and MoCl 4 and detected by laser-induced fluorescence. The room temperature depletion rate constant of Mo(a 5 S 2 ) + N 2 is (2.3 ( 0.7) × 10 -11 cm 3 s -1 ; the depletion rate constants of the a 5 D J are smaller and range from (16 ( 8) × 10 -12 for Mo(a 5 D 0 ) to (0.13 ( 0.04) × 10 -12 cm 3 s -1 for the other spin-orbit states. The depletion rate of all states of Mo by SO 2 are on the order of the collision rate. Mo(a 7 S 3 ) is found to be unreactive toward CO 2 , and the rate constant for the reaction of Mo(a 7 S 3 ) with N 2 O is expressed as k(T) ) (2.0 ( 0.5) × 10 -10 exp[-(9.8 ( 0.3) kcal mol -1 /RT] cm 3 s -1 . Termolecular kinetics are observed for Mo(a 7 S 3 ) + NO with k 0 ) (2.6 ( 0.3) × 10 -29 cm 6 s -1 , k ∞ ) (5.8 ( 0.5) × 10 -11 cm 3 s -1 , and F c ) 0.72 ( 0.07 at 296 K; the reaction rates for this reaction decrease with increasing temperature. Depletion rate constants of the reactions of the excited states of Mo with CO 2 , N 2 O, and NO are on the order of 10 -12 -10 -10 cm 3 s -1 ; the depletion kinetics are complex and involve significant energy transfers. Results indicate that the electron configuration of Mo plays a role in its depletion kinetics. In all cases, Mo(4d 5 5s 1 a 5 S 2 ) depletes faster than Mo(4d 4 5s 2 a 5 D J ). The inefficient reactions of Mo(a 7 S 3 ) with CO 2 and N 2 O are attributed to the production of spin-forbidden states.