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.