Rates of energy transfer from N2A3Σ +u to various molecules. Initial and final quantum states in the transfer to NOX2Π and Hg(61S0), and vibrational relaxation of N2A3Σ +u(v= 1) in helium

Abstract

A technique of monochromatic flash spectroscopy with the resonance radiations of Xe (1470 Å) and Kr (1236 Å) is described, with a quantal absorption of 1.4 × 10¹⁴ quanta cm^–3 per pulse. Production and decay of N₂A³Σ⁺_u(v= 0,1) was monitored photoelectrically from the sensitized fluorescence of either NO(γ-bands) or Hg (2537 Å) line. Rate coefficients for deactivation of N₂A³Σ⁺_u were recorded as k_Hg= 2.9 × 10^–10; k_C2H2= 1.6 × 10^–10; k_C2H4= 1.1 × 10^–10; k_NO= 8.0 × 10^–11; k_NH3 < 2 × 10^–11; k_N2O= 6.1 × 10^–12; k_O2= 3.6 × 10^–12; k_n-C4H₁₀= 2.7 × 10^–12; k_CO(N^*₂(v= 0))= 1.5 × 10^–12, k_CO(N^*₂(v= 1))= 2.4 × 10^–11; k_C3H8= 1.3 × 10^–12; k_C2H6= 3.6 × 10^–13; and k_H2= 3 × 10^–15 cm³ molecule^–1 s^–1; a significant difference in the rates of deactivation of the v= 0 and 1 states of N₂A³Σ⁺_u was found only for CO. Except in the transfer to NH₃ and Hg, the measurements agree well with those of Young et al.^1–5

In high pressures of He, vibrational relaxation of N₂A³Σ⁺_u(v= 1) was induced by collision prior to its deactivation, and a rate coefficient of 1.2 × 10^–15cm³ molecule ^–1 s^–1 was recorded. Correlation of initial and final quantum states was achieved for the transfer to NO, which populates predominantly A²Σ⁺(v= 0 and 1) : N₂A³Σ⁺_u(v= 0)+ NOX²Π(v= 0)→ N₂X¹Σ⁺_g+ NOA²Σ⁺(v= 1 : 0 = 1:9·5); N₂A³Σ⁺_u(v= 1)+ NOX²Π(v= 0)→ N₂X¹Σ⁺_g+ NOA²Σ⁺(v= 1:0 = 1:1·9). The results were analyzed with a model in which the transition probabilities are proportional to the products of the two Franck-Condon factors and the mean density of states associated with particular reaction channels. Transfer from N₂A³Σ⁺_u to Hg populates directly the Hg(6³P₀) state to the extent of about 25 %. From a comparison of the simultaneous NO γ and Hg 2537 Å emissions, it was suggested that excitation of NOA²Σ⁺ occurs with nearly unit efficiency. Excited atomic iodine (I5²P^½) was detected, via absorption of the 2060 Å line by kinetic spectroscopy, in the deactivation of N₂A³Σ⁺_u by CH₃I.