Mtd. Varella et al., CROSS-SECTIONS FOR ROTATIONAL EXCITATIONS OF CH4, SIH4, GEH4, SNH4 AND PBH4 BY ELECTRON-IMPACT, Zeitschrift fur Physik. D, Atoms, molecules and clusters, 39(1), 1997, pp. 59-67
We report differential and integral cross sections for rotational exci
tation of XH(4) molecules (X: C, Si, Ge, Sn, Pb) from 7.5-30 eV by ele
ctron impact. These cross sections were derived from fixed-nuclei scat
tering amplitudes (Bettega et al. 1995) obtained using the Schwinger M
ultichannel Method with Pseudopotentials (SMCPP) (Bettega et al. 1993)
. Our results represent the first rotational excitation cross sections
for molecules as large as GeH4, SnH4 and PbH4 using entirely ab initi
o procedures. The cross sections for CH4 and SiH4 obtained with pseudo
potentials are in very good agreement with all-electron calculations a
nd with other theoretical results. A comparison between our calculated
cross sections and experimental data for CH4 is in general encouragin
g, but some discrepancies remain. We found inelastic rotational cross
sections and momentum transfer cross sections to be larger for SiH4, G
eH4, SnH4 and PbH4 than for CH4. We could explain this feature.