Translational and rotational cooling in supersonic beams of OCS seeded in argon

Abstract

Translational and rotational relaxation in supersonic beams of OCS seeded in Ar was studied over a stagnation pressure-nozzle diameter product range of 5-140 torr·cm at stagnation temperatures of 295, 390, and 446 K. The relaxed translational distribution was measured by conventional time of flight (TOF) methods. The fraction of OCS molecules in the J = 1, MJ = 0 rotational state in that spatial and velocity group of the beam passed by electrostatic-state selectors was measured to probe rotational relaxation. These molecules were found to have an apparently greater J = 1, MJ = 0 population than that predicted by the full-beam translational temperature, indicative of a possible state-specific enhancement of rotational relaxation for molecules at the longitudinal flow velocity. © 1984 American Chemical Society.