The role of the electronic kinetic energy and its Cartesian components is examined during the formation of the ground (¹Σ), the first excited (¹Σ)^* and the lowest (³Σ) states of HeH⁺ employing wavefunctions of the multi-configuration type with, basis orbitals in elliptic coordinates. Results show, contrary to earlier beliefs, that the bond formation in these states is preceded primarily by a charge transfer from the neutral atom to the ion. There is no evidence of polarisation of the neutral atom orbitals by the ion even at large internuclear separation.

A few simple concerted radical-exchange reactions (A + BC →AB + C) are examined by the quantum-mechanicalab initio methods via calculations of bond orders and energies. Results reveal that, during these reactions, a small free valence develops on the migrating atom. As a result, the degree of bond-cleavage is more advanced than that of bond-formation with a common migrating atom at the transition state. The fact that bond-formation lags behind bond-cleavage is also examined by the configuration mixing of the reactant configurations at the early stages of the reaction.