Multiple ionization of gallium by electron impact

Abstract

A pulsed crossed-beam technique incorporating time-of-flight spectroscopy has been used to study the ionization of Ga by electrons at energies ranging from near threshold to 2100 eV. Relative cross sections for n-fold ionization where n = 1 to 4 have been normalized by reference to previous low-energy measurements of by Shul and co-workers based on a fast crossed-beam technique. Some large discrepancies have been noted between some of these and other previous measurements. Apart from some structure in the near-threshold behaviour of , the observed general lack of detailed structure in the multiple ionization cross sections is believed to be associated with the creation of many close-lying subshell vacancies. The measurements compare favourably with recent theoretical predictions based on semi-empirical scaling relations.

High-temperature mass spectrometry: Instrumental techniques, ionization cross-sections, pressure measurements, and thermodynamic data (IUPAC Technical Report)

“…For Zn, Cd, and Hg, the process was evidenced during determination of ionization efficiency curves near their thresholds [155]. A pulsed cross-beam technique incorporating time of flight spectroscopy [156][157][158][159][160][161][162][163][164][165][166] or related experimental procedures has been used since in additional studies of the ionization of several atoms.…”

Single and double ionization of gallium by electron impact

“…From a close inspection of the single ionization cross sections presented in table 1 by Patton et al [1] it is seen that there is a pronounced maximum of magnitude 11.0 ¢ 10 16 cm 2 at 27.1 eV impact energy. This maximum can be considered to arise from contributions of ionization of 4p and 4s shells whose binding energies are 5.6 eV and 11.54 eV respectively.…”

“…In particular, study of electron impact multiple ionization of atoms is of great importance in understanding astrophysical and fusion plasmas. Considering the relevance of reliable data on gallium to tokamak fusion devices, latest experimental measurements of single and multiple ionization cross sections for gallium have been carried out by Patton et al [1] using a pulsed crossed beam technique incorporating time of flight spectroscopy.…”

“…Fortunately the experimental measurements have been found to be in good agreement with the scaled cross sections. The calculations of single ionization cross section consider ionization of 4p and 4s shells only on the ground that the removal of a 3d electron leads to a large number of states whose energy exceeds the threshold for double ionization (see Patton et al [1]). Earlier, Vainshtein et al [5] compared their experimental measurements on gallium with the ionization cross sections calculated by different theoretical methods.…”

“…The above mentioned observations reflect some contributions of ionization of 3d shell to single ionization cross sections. At this stage we would like to recollect that single ionization cross sections have been calculated by empirical and semiclassical methods (see Patton et al [1]) whereas the double ionization cross sections have been determined by the scaling law proposed by Fisher et al [4]. To the best of our knowledge there has been no attempt to estimate the magnitudes of the contributions of ionization of 3d shell to single and double ionization cross sections.…”