AN AB-INITIO TREATMENT OF NEAR-THRESHOLD VIBRATIONAL-EXCITATION OF H2BY ELECTRON-IMPACT - NEW PERSPECTIVES ON DISCREPANCIES BETWEEN CROSSED-BEAM AND SWARM DATA

New crossed-beam measurements of the vibrational excitation cross sect ion Of H-2 are at variance with earlier determinations based on analys is of swarm data. This discrepancy poses a dilemma, as the modeling of a variety of plasma processes depends on cross sections derived from transport analysis. We present calculated cross sections for vibration al excitation of H-2 by low-energy electron impact using a fully ab in itio treatment of the electronic motion with incorporation of nonadiab atic nuclear effects through an approximate off-shell T-matrix formali sm. Our cross sections are in good agreement with recent data and are substantially larger than the values deduced from swarm data.