ELASTIC AND VIBRATIONALLY INELASTIC CROSS-SECTIONS AND ENERGY-LOSS SPECTRA FOR ELECTRON COLLISIONS WITH GEH4

Absolute vibrationally elastic cross sections for e-GeH4 collisions ha ve been determined for electrons of 1, 2, 2.5, 3, 5, 7.5, 10, 15, 20, 60 and 100 eV incidence energy over a scattering angular range of 10-d egrees-130-degrees. The observed angular distributions correspond, at least qualitatively, to theoretical formulations using the continuum-m ultiple-scattering method, the parameter-free static-exchange-polariza ton approximation, and a multichannel Schwinger variational calculatio n. Vibrational excitation functions and the energy distribution of ela stically scattered electrons reveal a shape resonance at about 2-2.5 e V. Calculations show that the resonance scattering state belongs to th e t2 representation of the T(d) point group, which is also the represe ntation of the lowest unoccupied molecular orbital (LUMO) of GeH4. Ene rgy loss spectra recorded in the electronic threshold region of GeH4 r eveal enhanced inelastic scattering at large angles in the loss range 7-9 eV characteristic of excitation to the lowest triplet state.