Theory of chemical reactions of vibronically excited H2(B 1Σ+u). I. Prediction of a strongly bound excited state of H4

Abstract

MRD–CI calculations were carried out on the potential energy surfaces of the ground and first excited singlet of the same symmetry of H₄, which predict a bound excited state with respect to H₂+H^*₂ (B ¹Σ⁺_u) of 3.1 eV at a geometry of trigonal pyramid. This geometry was predicted theoretically according to a model of chemical bonding for ‘‘maximum ionicity excited states.’’ At the minimum and the three dimensional space surrounding it, there is a near touching of the excited with the ground state hypersurfaces. This fact has implications for the spectroscopy and photochemistry of the H₂+H^*₂ system.