Dissociative recombination of interstellar ions: electronic structure calculations for HCO/sup +/

The present study of the interstellar formyl ion HCO/sup +/ is the first attempt to investigate dissociative recombination for a triatomic molecular ion using an entirely theoretical approach. We describe a number of fairly extensive electronic structure calculations that were performed to determine the reaction mechanism of the e-HCO/sup +/ process. Similar calculations for the isoelectronic ions HOC/sup +/ and HN/sub 2//sup +/ are in progress. 60 refs

ROTATIONAL EXCITATION OF CO BY He IMPACT

To study rotational excitations of CO by He impact, configurationinteraction potential energy surfaces have been computed with two different basis sets. The surfaces are compared to one another, to an electron-gas surface, and to an experimentally determined surface. In addition, converged close-coupling calculations of the collision cross sections have been done on these surfaces for energies up to 100 cm{sup -1} and compared. On the most accurate CI surface, cross sections have been computed using the infinite-order sudden (IOS) and quasi-classical methods as well

An ab initio study of the rotation—vibration energy levels of GeH2 in the ā3B1 state

Thirty-five points on the potential energy surface of the ā3B1 first excited state for the GeH2 radical have been calculated using the (ab initio) MRD CI technique. Thirteen parameters in an analytic expression for the potential have been adjusted (by least-squares optimization) so that the surface fits these points. The rotation-vibration energy levels of GeH2. GeD2 and GeHD have been calculated using the non-rigid bender Hamiltonian, and we determine for GeH2 that ν1 = 1991 cm-1. ν2 = 763 cm-1, and ν3 = 2012 cm-1. The equilibrium structure is found to be re = 1.545 Å and αz = 119.8°, and the singlet-triplet splitting is calculated to be 22.8 kcal/mole (7975 cm-1)