L. Bewig et al., PHOTON AND ELECTRON-IMPACT FRAGMENTATION OF SIZE-SELECTED SODIUM CLUSTERS, Zeitschrift fur Physik. D, Atoms, molecules and clusters, 26, 1993, pp. 104-106
We investigate the fragmentation behaviour of size selected sodium clu
sters Na(n), n less-than-or-equal-to 5, for different ionization metho
ds. The experimental technique, size selection by means of scattering
the cluster beam from a helium target beam, enables us to find a uniqu
e correlation between the detected cluster ions and their neutral prec
ursors. In the case of photoionization we use the light from a Xe-arc
lamp in a broad spectral range down to a wavelength of about 220 nm, w
hereas for the pulsed, frequency doubled dye laser the wavelength is t
uned to 265 and 290 nm. Electron impact ionization has been examined w
ith an electron energy of 25 eV. The ionization by electron impact wit
h the large excess energy results in a total fragmentation of the sodi
um trimer. In the case of photoionization the fragmentation probabilit
ies depend sensitively on the excess energy.