Temperature dependent quenching of the A 2Σ+ and B 2Π states of NO

Collisional quenching of the v′=0 vibrational levels of the A 2Σ+ and B 2Π states of nitric oxide has been studied over the temperature range 300 to 750 K. The pressure dependence of the time decay of laser-induced fluorescence, in a slowly flowing heated cell, furnished the quenching cross sections σQ. NO and O2 quench the A state rapidly but with no temperature dependence; σQ=37 and 21 Å2, respectively. σQA for H2O drops from 105 Å2 at 300 K to 34 Å2 at 750 K. σQB for O2 is independent of temperature but σQB for NO drops twofold and for H2O decreases by a factor of 3 over the temperature range studied. This variation among these colliders cannot be explained by a uniform, simple picture of the collision dynamics. Evidence is seen for B→A transfer proceeding through an intermediate state, perhaps a 4Π.