Generalization of the nonlocal resonance model for low-energy electron collisions with hydrogen halides: the variable threshold exponent

The nonlocal resonance model developed previously for the description of lo w-energy electron collisions with hydrogen halides is generalized to includ e the dependence of the dipole-modified threshold exponent on the internucl ear distance. An efficient computational scheme has been developed to deal with the resulting nonseparability of the nonlocal complex potential for th e nuclear motion within the Schwinger-Lanczos approach. The results reveal that the R-dependence of the threshold exponent has a significant effect on the threshold peaks in the vibrational excitation cross sections of HCl. T he shape and intensity of the calculated threshold peak in the 0 --> 1 vibr ational excitation channel, in particular, are in much better agreement wit h experimental data than previous results. For the electron-HBr and electro n-HI collision systems the effects of the R-dependence of the threshold exp onent are not significant.