Emission by collisional H-2-He pairs at temperatures from 2 to 20 kK

The dipole surface of H-2-He collisional pairs is computed from first princ iples for 20 intramolecular spacings of the H-2 molecule, from 0.6 to 4 Boh r; 11 separations of the H-2-He pair, from 2 to 6 Bohr; and five values for the angle subtended by the intramolecular and intermolecular axes. From th is dipole surface, the dipole matrix elements are obtained for all possible rotovibrational transitions \vJ >--> v'J'>, with v and v'=0,... ,14. Subse quently, the collision-induced emission spectra are computed for frequencie s from 100 to 100 000 cm(-1), at temperatures of thousands of Kelvin-a rang e believed to be important for various light sources of high gas densities, such as the atmospheres of "cool" stars, shockwaves, flames, rocket jets, etc. We find that at the lower temperatures considered, radiation is emitte d mostly in the fundamental band of H-2, while at high temperatures the col lision-induced emission spectra extend into the visible, with overtone tran sitions involving large Delta v=v-v'. (C) 1999 American Institute of Physic s. [S0021-9606(99)30638-3].