Determination of rates of collision-induced vibrational and intramultiplet transitions for YO(A2II) molecules in Ar- and N2-diluted flames

Abstract

Abstract Rate contants for single-step collisional transitions between specified vibrational and electronic-doublet levels of YO(A 2 II) molecules were determined under multiple-collision conditions at constant total gas pressure. We recorded simultaneously the thermal emission spectrum and the fluorescence spectra induced by a cw dye laser tuned successively at various vibronic transitions. We used premixed N 2 -diluted or Ar-diluted H 2 -O 2 flames at 1 atm and = 2350 K, containing YO vapour. Relative rate constants (normalized to the quenching plus radiative de-excitation rate constants) were obtained by solving a set of simultaneous master equations involving the stationary laser-induced population increments. Absolute rate constants were derived therefrom by determining indirectly the fluorescence efficiency. Exoergic doublet-mixing collisions appeared to have greater probabilities than Δ v = −1 or −2 transitions and were about equally probable as quenching collisions. Ar and N 2 were about equally efficient as collision partner. The rate constants of each process and of its reverse were compared with detailed-balance. The rotational levels in the pumped band appeared to preserve the e/f symmetry index partially.