Ultraviolet laser photodesorption of NO from condensed films: Translational and internal energy distributions

In this paper we report that ultraviolet laser induced desorption from the surface of a thin nitric oxide film proceeds via two mechanisms which are present simultaneously. One mechanism is attributed to laser induced thermal desorption while the other is due to a nonthermal, single photon process. A film of 1–2000 ML (layers) of NO condensed on a Ag(111) substrate under UHV conditions at 25–50 K was irradiated by 5 ns pulses of 220–270 nm laser light (4.6–5.5 eV) with 0.5–5 mJ/cm2 (0.1–1 MW/cm2 ) power density at the surface. Translational energies of desorbed molecules were measured from time‐of‐flight (TOF) spectra taken with a mass spectrometer, while the internal energy distribution of molecules desorbed in the nonthermal channel was determined by a (1+1) resonance enhanced multiphoton ionization (REMPI) probe. NO monomer in the 2Π3/2,1/2 electronic ground states was the only significant product. There were two distinct characteristic TOF components, which we associate with different desorption mecha...

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