State-to-state cross sections and a survey of detailed balance for transitions among the vibrational and rotational (v; j) states of H2 1Pg+ below 37 mEh as the result of collisions in the H2 + H2 system were determined by using the quasiclassical trajectory (QCT) method. Study of this system is necessary for an improved under-standing of the kinetics in the interstellar medium to model processes occurring in the molecular clouds. The potential energy surface of Boothroyd et al. (J. Chem. Phys. 116, 666, 2002) was used for trajectory calculations. The Discrete Variable Explicit Runge-Kutta (DVERK) method was used for numerical integration. State-to-state cross sections were examined for agreement with microscopic reversibility. In the majority of cases the agreement was poor. Consequently the conclusion is that QCT is not a viable method for the evaluation of state-to-state rate coefficients in the H2 + H2 system.
