ABSTRACTEmission of ionic clusters from surfaces of group IV elements has been analyzed by means of time-of-flight measurements under nitrogep laser irradiation in its peak intensity ranging from 50 to 200 MW/cm with pulse duration of 10 ns. The measurements on Si, Ge and β-Sn with a straight flight tube show a continuous distribution of spectra in the flight time corresponding to the mass-to-charge ratio between 1 and 2 in units of the singly charged atom of respective elements. The line shape analysis indicates that emitted ions immediately after laser excitation are coagulated in the form of large clusters having nearly an equal mass-to-charge ratio between 5/4 and 3/2. They eventually decompose into monoatoms and their ions in a time scale of 10 ps as confirmed by a quadrupole mass analysis. These results are in remarkable contrast with the case of graphite which exhibits a series of sharp spectral peaks. The clear distinction between graphite and other group IV elements is attributed to the intrinsic difference in their chemical bonds under highly excited conditions.
Phthalocyanine-modified silica gels and their application in the purification of unsymmetrical phthalocyanines