Evidence for thermalization of surface-desorbed molecules at heating rates of 108 K/s

Laser desorption of aniline-d7 from a single-crystal surface 0001 of sapphire Al2O3 at a heating rate on the order of 108 K/s was studied using pulsed infrared laser radiation for desorption and resonance enhanced multiphoton ionization REMPI for detection of the desorbed aniline molecules. On the basis of single-vibronic-level fluorescence SVLF spectra we unambigiously assign the 10b transition. REMPI spectroscopy provides vibrational temperatures and therefore describes the internal energy distribution, whereas the time-of-flight TOF profiles provide translational temperatures. All results are consistent with a thermal mechanism for desorption, i.e., pulsed heating of the sapphire surface on the nanosecond time scale leads to thermal desorption and rapid thermalization of the escaping molecules. © 1996 American Institute of Physics. S0021-9606 96 01121-X