Potential energy surfaces for the collinear H3+ system

Approximate potential energy surfaces for the two lowest singlet states of collinear H3+ are computed using the diatomics-in-molecules (DIM) approach. Permanent dipole moments for these states and transition dipole moments between them are computed analytically in this approximation. These potential surfaces and dipole functions are essential for a realistic description of the interaction between the H3+ and a strong external optical field. The computed results show the correct asymptotic behavior as the inter-nuclear distances in H3+ become large and are in good agreement with an accurate ab initio calculation but are not currently available as a complete package, either in the literature or from existing ab initio quantum-chemistry softwares.