Collisional removal of OH(X (2)pi,nu=7) by O-2, N-2, CO2, and N2O

Collisional removal rate constants for the OH (X (2) Pi,nu=7) radical are measured for the colliders O-2, CO2, and N2O, and an upper limit is established for N-2. OH(nu=4) molecules, generated in a microwave discharge flow cell by the reaction of hydrogen atoms with ozone, are excited to nu=7 by the output of a pulsed infrared laser via direct vibrational overtone excitation. The temporal evolution of the nu=7 population is probed as a function of the collider gas partial pressure by a time-delayed pulsed ultraviolet laser. The probe laser light is resonant with the (0,7) band of the B (2) Sigma(+)-X (2) Pi transition. Fluorescence from the B (2) Sigma(+) state is detected in the visible spectral region, We measure rate constants for CO2, (6.7+/-1.0)x10(-11) N2O, (3.0+/-0.6)X10(-11) O-2, (7+/-2)X10(-12); and N-2, <6x 10(-13) (all in units of cm(3) s(-1)). (C) 1996 American Institute of Physics.