Is Infrared Laser-Induced Desorption a Thermal Process? The Case of Aniline

A complete study of nanosecond laser-induced thermal desorption (LITD) of aniline submonolayers from silica as well as nanosecond and picosecond laser desorption from glassy graphite was undertaken. The measurements include determination of equilibrium desorption kinetic parameters; time-resolved studies on the surface temperature and the surface coverage during laser heating; and investigation of translational, vibrational, and rotational temperatures of laser-desorbed molecules. Our findings are that LITD of aniline up to heating rates of 1010 K/s is consistent with complete thermalization of the molecules during fast desorption. At 1013 K/s, only the kinetic energy of the desorbed molecules agrees well with a thermal desorption model, whereas the internal degrees of freedom are not fully equilibrated, but appear to be somewhat colder.