Deactivation rate constants of OH(X-2 Pi(i), v=1-4) by collisions of NH3

Collisional deactivation of OH(X(2)Pi, nu = 1-4) by NH3 has been studied us ing pulsed laser photolysis coupled with the pulsed laser probe technique. Mixtures of O-3/NH3/N-2 were photolyzed at 248 nm, and time-resolved OH pop ulations were monitored via the Delta nu = 0 and -3 sequences of the A(2)Si gma (+)-X(2)Pi (i) transition. The following deactivation rate constants at 298 +/- 1 K were obtained: (2.9 +/- 0.2) x 10(-11) for nu = 1, (1.1 +/- 0. 2) x 10(-10) for nu = 2, (3.4 +/- 0.4) x 10(-10) for nu = 3, and (4.1 +/- 0 .3) x 10(-10) for nu = 4 in units of cm(3) molecule(-1) s(-1) (the errors a re 2 sigma). The present study is the first report on the rate constant for OH(nu = 4) + NH3 reaction. The deactivation of OH(nu less than or equal to 3) by NH3 can be elucidated by nonresonant V-V energy transfer caused by l ong-range interaction; that of nu = 4 deviates from the gap law.