Abstract: The present paper covers ab initio UHFcalculations with a d, p-polarized basis set performed for eight electronic states of BH₂ and the equilibrium geometries, electronic term values Tc and vibrational frequencies of the five stable states X²A₁, ²B₁, ²B₂, 2²A₁ and ²A₂. On the basis of the UHFresults, the states 2²B₂. ²B₁ and 3²A₁ are predicted to be unstable. The MP₂/6-31G^** calculations were performed for the X²A₁ and ²B₁, states, and the calculated equilibrium geometries, Tc value and vibrational frequencies are similar to the UHFresults. The MP₂/6-31G^** studies on the reaction BH₂→BH + H for the X²A₁ and ²B₁ states were carried out and the HB-Hbond energies of these two states were calculated.

Key words: Ab initio calculation, Electronic excited state, Borane(Ⅱ)