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 CD 3 F condensed on the NaCl(100) single crystal surface, in which the intramolecular vibrations of the CD 3 F 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 mm, corresponding to excitation on the n 2 , n 3 , n 5 , and n 6 modes of CD 3 F. An analysis of the time-of-flight spectra as a function of the laser fluence is presented. Different desorption mechanisms are discussed.

Free-electron laser induced processes in thin molecular ice

“…Collisions occurring between photodissociation products and ice constituents are central to the formation of new species. Furthermore, even without reactions, such energetic collisions will lead to the desorption of neutral species from the ice layer, as has been observed for vibrational resonant IRinduced desorption from molecular ices, like N2O, 51,52 CD3F, 53 and methane. 54 …”

Resonant infrared laser-induced desorption of methane condensed on NaCl(100): Isotope mixture experiments

“…[9][10][11] In the present investigation, we report results on desorption experiments of methane condensed on NaCl͑100͒. Experiments are performed with three methane isotopologues-CH 4 , CD 4 , and CD 3 H-as well as with mixed layers of these isotopes.…”

“…Recently it has been shown that a free-electron laser ͑FEL͒ operating in the infrared is a wellsuited radiation source for this kind of investigations. [9][10][11] Theoretical studies of desorption by laser-adsorbate vibrational coupling and energy transfer have been carried out, [12][13][14][15][16][17] particularly for the well-investigated physisorption system CO / NaCl͑100͒. 18,19 In the present work the infrared laser-induced desorption of different methane isotopologues condensed on a NaCl͑100͒ single-crystal surface is investigated using the FEL of the free-electron laser for infrared experiments ͑FE-LIX͒ facility in the Netherlands as the excitation source.…”

Photoinduced Processes of Solid Aromatic Compounds by Mid-IR Free Electron Laser

“…Extensive studies have been performed in a wide range of wavelengths from UV to IR. [1][2][3][4][5][6][7][8] A UV laser induces a process to promote atoms and molecules efficiently to highly excited states, resulting in photochemical reactions. [9][10][11][12] On the other hand, it is generally accepted that photothermal processes are dominant in the case of IR laser irradiation; the irradiation causes heating of the target by a rapid vibrationalenergy relaxation in a solid in 5 -10 ps.…”

“…13) It provides an intense MIR pulse with a tunable wavelength and a picosecond or subpicosecond duration, and is thus a promising tool for investigating the laser-induced processes in the MIR region. According to recent laser-induced desorption studies, MIR-FEL irradiation induces a thermal desorption of small molecules condensed on low-temperature substrates: 7,8) Condensed N 2 O and CD 3 F molecules on NaCl substrates are vibrationally excited by the resonant absorption of FEL photons. The vibrational energy of the adsorbates transfers to the substrate, thereby heating the substrate.…”