Resonant infrared laser-induced desorption of CD3F condensed on NaCl(100)

Abstract

In investigations of the dynamics of the desorption of molecules from surfaces, a selective excitation of specific molecular vibrations is desirable. We here report studies on the infrared laser-induced desorption of CD₃F condensed on the NaCl(100) single crystal surface, in which the intramolecular vibrations of the CD₃F molecules are directly excited. Desorption of the intact molecules is monitored using electron impact ionization followed by mass-selective detection in a quadrupole mass spectrometer. Desorption only occurs when the excitation laser is at 9.0, 10.5, 9.4, or 11.0 µm, corresponding to excitation on the ν₂, ν₃, ν₅, and ν₆ modes of CD₃F. An analysis of the time-of-flight spectra as a function of the laser fluence is presented. Different desorption mechanisms are discussed.