Depletion Kinetics of Niobium Atoms in the Gas Phase

Abstract

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.

Reactivity of niobium clusters with nitrogen and deuterium

“…Similar unimolecular reaction theory calculations were used to estimate k 0 for the reaction of the Nb atom with N 2 . McClean et al 18 have reported k 0 ϭ(2.6Ϯ0.3) ϫ10 Ϫ32 cm 6 s Ϫ1 for this reaction in Ar buffer gas at 296 K. Using the theoretically predicted properties of NbN 2 described in Sec. III B, we calculated k 0 ϭ1.3 ϫ10 Ϫ31 cm 6 s Ϫ1 , assuming strong collisions.…”

Depletion kinetics of low-lying states of tungsten in the presence of NO, N2O, and SO2

“…character [4]. Experiments with vanadium [6], titanium [3,7], molybdenum [2,17], and niobium [25] have been performed recently which generally support this model.…”

Reaction dynamics of Mo + O2 → MoO + O studied by a crossed-beam velocity map imaging technique

“…1 For this reason, a fair amount of kinetic studies have been carried out for reactions of gas-phase neutral transition metal atoms with small oxygen-containing molecules (OX). [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] In several studies, the reaction rate constants for some low-lying electronically excited states 21 have been determined, as well as those for the ground states. 2-7, 11, 14-16 Although the excited states usually showed larger reaction rate constants than the ground states, some studies showed higher reactivities of the ground states, and suggested that the electron configuration plays a more important role than the energy.…”

“…2-7, 11, 14-16 Although the excited states usually showed larger reaction rate constants than the ground states, some studies showed higher reactivities of the ground states, and suggested that the electron configuration plays a more important role than the energy. 15,16 To understand the oxidation reactions of the transition metal atoms, two reaction mechanisms have been proposed. One is a direct oxygen abstraction mechanism.…”