Survival of HCl(nu=2) in trapping-desorption from MgO(100)

An HCl molecular beam incident on MgO(100) is photoexcited to v = 2, J = 1 by using a pulsed parametric oscillator. At a translational energy of 0.11 eV, incident HCl is adsorbed. Thermal desorption yields v = 2 molecules who se rotational and translational degrees of freedom are equilibrated at the surface temperature. Surface residence times for v = 2 might be as long as 1 mu s. At 180 K, it is concluded that a large fraction of surface-bound v = 2 molecules reenter the gas phase, while at 120 K, deactivation exceeds d esorption by an order of magnitude. Deactivation probably takes place at st eps. (C) 2000 Elsevier Science B.V. All rights reserved.