T. Ruhaltinger et al., ANOMALOUS VIBRATIONAL-EXCITATION IN THE SMALL-ANGLE SCATTERING OF HE-60 EV( FROM HCL AT E(LAB)=20), Journal of physical chemistry, 99(42), 1995, pp. 15544-15550
Energy loss spectra of forward scattered He+ ions in collisions with H
Cl are reported for collision energies (E(lab)) in the range 20-60 eV.
The spectra extend up to total energy transfers of about 2.5 eV, wher
e the intensity is 6 orders of magnitude less than the elastic forward
peak. At large energy transfers a number of broad maxima indicating a
propensity for large Delta v transitions are observed. Three-dimensio
nal quasiclassical trajectory calculations treating HCl as a rigid rot
or for the long range ion-dipole/quadrupole He+-HCl interaction and a
short range repulsion corresponding to the isoelectronic He+-Ar accoun
t for much of the energy transfer at low Delta E. At higher Delta E, t
he rigid rotor model is dearly inadequate and a better description of
the experiment requires consideration of high lying repulsive states o
f HCl+ which appear to be temporarily accessed by charge transfer.