Journal of Physical Chemistry, Vol.100, No.21, 8901-8906, 1996
An Upper Limit on the Formation of No(X(2)Pi(R)) in the Reactions N-2(A(3)Sigma(U)(+))+o(P-3) and N-2(A(3)Sigma(U)(+))+o-2(X(3)Sigma(G)(-)) at 298K
The concentration of the product nitric oxide, [NO(X(2) Pi(r))](product), formed in the title reactions is measured as a function of the vibrational energy distribution in the N-2(A(3) Sigma(u)(+)) for v’ less than or equal to 6 in a rapidly pumped discharge-flow reactor at similar to 298 K and a total pressure of similar to 2 Torr using laser-excited fluorescence techniques. For the reaction N-2(A(3) Sigma(u)(+), v’ less than or equal to 2) + O(P-3) there is no [NO(X(2) Pi(r))](observed) detected above the noise in the background emission signal. Correcting this null measurement for competing reactions, the NO(X(2) Pi(r)) + N((SD)-S-4-D-2) product yield accounts for less than or equal to 2% (signal-to-background noise = 1, 1 sigma) of the [N-2(A(3) Sigma(u)(+),v’)](total). For the reaction N-2(A(3) Sigma(u)(+),v’ less than or equal to 6) + O(P-3) the [NO(X(2) Pi(r))](observed) is seen to increase slightly relative to the reaction N-2(A-(3) Sigma(u)(+),v’ less than or equal to 2) + O(P-3). Correcting the [NO(X(2) Pi(r))](observed) for competing reactions, the NO(X(2) Pi(r)) + N(S-4,D-2) product yield accounts for 5.7 +/- 1.1% of the [N-2(A(3) Sigma(u)(+))](total) and as much as 57 +/- 14% of the [N-2-(A(3) Sigma(u)(+),3 less than or equal to v’ less than or equal to 6)]. For the reaction N-2(A(3) Sigma(u)(+), v’ less than or equal to 6) + O-2(X(3) Sigma(g)(-)) no [NO(X(2) Pi(r))](observed) is detected above the noise in the background emission signal. Correcting this null measurement for competing reactions, the NO(X(2) Pi(r)) + NO(X(2) Pi(r)) product yield represents <0.1% of the [N-2(A(3) Sigma(u)(+),v’)](total). Possible implications of these observations are discussed.
Keywords:ENERGY-TRANSFER-REACTIONS;METASTABLE ARGON ATOMS;RATE CONSTANTS;VIBRATIONAL-RELAXATION;MOLECULES;O-2;NO;DEACTIVATION;EXCITATION;NITROGEN