Abstract: In this paper, the variational transition state theory is extended to calculate the state-selected reaction rate constants for an arbitrarily assigned vibrational excited reactants and their transition state. The extended theory can be used to calculate the rate constants for a series reactions of H+H₂(v) and its isotopic analogues through different vibrational excited transition states. In comparison of the calculated results with experimental values, it is found that the results obtained by the exciting bend vibration modes are nuch close to the experimental values. It is also first obtained that when an energy is given, the exciting transition state's bend modes are more favourable to the reactions than the exciting stretch ones.

Key words: Variational transition state theory, H+H₂, State-selected, Vibration modes