The excitation of IF(B 3Π0+) by N2(A 3Σ+u)

Abstract

Experiments in a discharge‐flow reactor show that the energy‐transfer reaction between N₂(A ³Σ⁺_u ) and IF(X ¹Σ⁺) is extremely rapid (k_total=2.0×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹) with 40% of the quenching collisions resulting in fluorescence from IF(B ³Π_0⁺).The reaction populates IF(B) vibrational levels up through v’=9 and produces v’=0–6 with about equal probability at low pressure. The vibrational distribution relaxes rapidly in collisions with the reactor bath gas even at pressures of a few Torr. The vibrational relaxation rate coefficients for levels 3–6 of IF(B) in a mixture of 80% Ar/20% N₂ are about 3×10⁻¹² cm³ molecule⁻¹ s⁻¹, with levels 1 and 2 being a little slower. Differences in IF excitation between N₂(A) v’=1 and v’=0 are small (k_v’=1/k_v’=0≤1.2). Electronic quenching of the IF(B) is sufficiently slow that even at higher reactor pressures radiative decay is the dominant loss. Rate coefficients for quenching N₂(A), by CF₃I, and NF₃ and for vibrational relaxation of N₂(A,v’=1) by CF₄, CF₃H, CH₄, and SF₆ also are reported.