EVIDENCE FOR THERMALIZATION OF SURFACE-DESORBED MOLECULES AT HEATING RATES OF 10(8)-K S/

Laser desorption of aniline-d7 from a single-crystal surface (0001) of sapphire (Al2O3) at a heating rate on the order of 10(8) K/s was stud ied usin,g pulsed infrared laser radiation for desorption and resonanc e enhanced multiphoton ionization (REMPI) for detection of the desorbe d aniline molecules. On the basis of single-vibronic-level fluorescenc e (SVLF) spectra we unambigiously assign the 10b transition. REMPI spe ctroscopy provides vibrational temperatures and therefore describes th e internal energy distribution, whereas the time-of-flight (TOF) profi les provide translational temperatures. All results are consistent wit h a thermal mechanism for desorption, i.e., pulsed heating of the sapp hire surface on the nanosecond time scale leads to thermal desorption and rapid thermalization of the escaping molecules. (C) 1996 American Institute of Physics.