Desorption and Decomposition of Multiply Charged Clusters from the Crystal of Group IV Elements by Laser Excitation
Dynamical aspects of ion desorption from the solid target of group IV elements by laser excitation have been investigated by means of a time-of-flight spectrometer, a 127° electrostatic energy analyzer and of a quadrupole mass spectrometer. The mass distribution of emitted clusters and their decomposition times depend considerably on the wavelength and intensity of exciting laser beam. Our TOF spectrum on graphite by N2 laser excitation shows a series of sharp lines at the flight times for C3i 2+ clusters (i= 1 to 7). The results on the excitation by excimer lasers of KrF and ArF, on the other hand, show band spectra for the peaks with i = 1 and 3. The spectral profile is; quite similar to that observed in Si by N2 laser excitation. Hence, the spectral broadening for peaks with i = 1 and 3 is caused by their decompositions in the time scale of 100 ns. For quadrupole mass analysis, the dominant species is identified with C+ 3 for N2 and KrF and С for ArF. The measurements of photo-electron energy distribution gives the average kinetic energy in the order of 1 eV for the excited electrons in the solid. This kinetic energy becomes higher for the laser excitation in order of increasing photon energy from 3. 68 eV (NL) to 5. 0 eV (KrF) to 6. 4 eV (ArF).
KeywordsLaser Excitation Flight Time Graphite Surface Average Kinetic Energy Kinetic Energy Distribution
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- 1.J. F. Ready, Effects of High Power Laser Radiation (Academic Press, New York, 1971) Chap 4.Google Scholar