STP1015

    Temporal Distribution of Electron and Ion Emission Caused by Laser Excitation of Optical Surfaces in Ultra-high Vacuum

    Published: Jan 1988


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    Abstract

    We have measured electron and ion emission under high vacuum conditions from several semiconductor and insulator surfaces excited by the first and third harmonics of a 1.06 μm Nd laser. The dependence of this emission on laser fluence and wavelength is consistent with a multiphoton excitation process. The dependence on laser pulse length implies, however, that other processes, either diffusive, thermal or thermomechanical, are also involved. Additional information is provided by the temporal and spatial distribution of the charge emission. The most extensive results have been obtained with single crystals of ZnS, for which nearly equal magnitudes of negative and positive charge emission are observed. The results suggest the possibility that the observed charge emission results primarily from the ejection of neutral atoms and molecules from the surface, followed by selective multiphoton ionization of one or more of the neutral species. The irreversible surface modification implied by the observed emission may be the precursor to observable surface damage. Detailed studies of the properties of the emitted particles may be very useful in developing a basic understanding of the damage mechanisms.

    Keywords:

    damage precursors, electron and ion emission, multiphoton ionization


    Author Information:

    Siekhaus, WJ
    Lawrence Livermore National Laboratory, Livermore, California

    Chase, LL
    Lawrence Livermore National Laboratory, Livermore, California

    Milam, D
    Lawrence Livermore National Laboratory, Livermore, California


    Paper ID: STP18797S

    Committee/Subcommittee: F01.11

    DOI: 10.1520/STP18797S


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