Wavelength-selective laser desorption of doped ice surfaces

We present a visible/infrared comparative photo-desorption study of several metal salt/ice binary mixtures. The cryogenic samples have been successively irradiated by a frequency-doubled (532 nm) Nd:YAG laser and a 3.1 μm LiNbO3 optical parametric oscillator. The desorbed neutrals have been post-ionized by the focused beam of a frequency-quadrupled Nd:YAG laser at 266 nm (4.7 eV) and the ions produced have been mass-separated by a reflectron time-of-flight mass spectrometer. Wavelength-selective desorption has been evidenced for all the mixtures considered. This behaviour is tentatively explained with respect to the absorption spectra of these systems. The evolution with the desorption laser fluence and the solution concentration has also been investigated. Possible laser cleaning practical implications are discussed and illustrated by the application to a combustion soot particles/ice system.