presented in VUV-12, San Francisco, Aug 1998.
Exciton induced desorption of excited atoms in 2p53p state from solid Ne
Takato HIRAYAMA1, Kazuyoshi IMOTO1, Takashi ADACHI1, Akira HAYAMA1,
Ichiro ARAKAWA1, Koichiro MITSUKE2, and Makoto SAKURAI2
1Department of Physics, Gakushuin University, Toshima Tokyo 171-8588 JAPAN.
2Institute for Molecular Science, Myodaiji, Okazaki 444-8585 JAPAN.
Desorption of excited atoms from the surface of rare gas solids (RGSs) by the creation of excitons has been extensively studied in these 10 years[1]. Most of the experimental results have been well described in the framework of two proposed desorption mechanisms, cavity ejection (CE) and excimer dissociation (ED).
Figure 1(a) shows time-of-flight (TOF) spectra of metastable atoms in 2p53s (3P0,2) states desorbed via CE process (Ne*[CE]) from the surface of solid Ne, and fig.1(b) shows a dependence of Ne*[CE] desorption yield on the wavelength of the incident VUV light in the energy range corresponding to the excitation of 2p53p-type surface exciton (S'). The wavelengths where each TOF spectrum was measured are marked by open circles in fig.1(b). The shift of the peak position as a function of the wavelength (dashed line in fig.1(a)) is likely due to the ten different energy levels in 2p53s configuration. This result is in consistent with the cavity ejection scheme, i.e., the kinetic energy of desorbed atoms depends on the repulsive interaction between an excited atom and the surrounding ground state atoms.
Desorbed 2p53p atoms are known to decay to 2p53s states by emitting visible light in vacuum. Figure 2 shows a 3p -> 3s fluorescence spectrum of Ne* atoms in 2p53p states desorbed from solid Ne by electron impact with the incident energy of 89eV. By the selective excitation of S' excitons using monochromatic VUV light, we have obtained similar fluorescence spectra with lower resolution because of low intensity of incident photon.
The aim of the present study is the measurements of TOF spectra of desorbed metastable atoms in coincidence with the 3p -> 3s fluorescence, from which we expect to get the detailed information on the correlation between the initial excitation and resulting desorption dynamics. The detailed discussion will be presented at the conference.
1. I. Arakawa, in Molecular Crystals and Liquid Crystals, (Gorden and Breach Science Publishers, New York, 1998) to be published, and references therein.
Fig.1. (a) Time-of-flight spectra of Ne*[CE] desorbed from the surface of solid Ne. (b) Ne*[CE] desorption yield as a function of the wavelength of the incident light.
Fig.2. Fluorescence spectrum from desorbed Ne* by electron impact (excitation energy: 89eV). Each line corresponds to 2p53p -> 2p53s deexcitation in gas phase.
PDF file of the poster presented in the conference.
