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

Experiments in a discharge-flow reactor show that the energy-transfer reaction between N2(A 3Σ+u ) and IF(X 1Σ+) is extremely rapid (ktotal=2.0×10−10 cm3 molecule−1 s−1) with 40% of the quenching collisions resulting in fluorescence from IF(B 3Π0+).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 (kv′=1/kv′=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.