Potential-energy curves of six ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$, two ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }$, and one ${}_{}{}^1{}_{}{}^{}\mathrm{\Delta }$ states have been determined for the ${\mathrm{N}}^{5+}$+He→${\mathrm{N}}^{4+}$+${\mathrm{He}}^{+}$ process by means of ab initio calculations with configuration interaction. The matrix elements of the operator d/dR between the four ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$ states and the two ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }$ states involved in the collisional process have been calculated by the rigorous finite-difference technique. A very peaked radial coupling matrix element is observed at 8.30 a.u. corresponding to an avoided crossing between the entry channel and the ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$ state dissociating to {${\mathrm{N}}^{4+}$(3d)+${\mathrm{He}}^{+}$}. Two other avoided crossings between ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{}^{+}{}_{}{}^{}$ states are observable at 7.50 and 6.35 a.u. Rotational and radial couplings involving ${}_{}{}^1{}_{}{}^{}\mathrm{\Pi }$ states have also been determined.

• Received 2 March 1987

DOI:https://doi.org/10.1103/PhysRevA.36.1994