Rotational-level-dependent quenching of A 2Σ+ OH and OD

Rate constants kQ for collisional quenching of A 2Σ+, v′=0, OH and OD have been measured for specific rotational levels N′ of the radical and a wide variety of collision partners. Through measurements of the time-dependent laser-induced fluorescence in a low pressure discharge flow at room temperature, we observe a decrease in kQ with increasing rotational quantum number for most quenchers. The internal levels of the collision pairs appear unimportant from experiments involving deuterium substitution. A comparison of rotationless rates for different colliders [kQ(N=0)] with calculations based on collision complex formation indicate that attractive forces play a role in the quenching process.