The collinear Cl + XY system (X,Y=H,D,T). A comparison between quantum mechanical, classical, and transition state theory results

In this work, exact quantum mechanical (QM) and classical (CL) transition probabilities for the Cl+XY (X,Y=H,D,T) collinear system are compared. The calculations were performed using a semiempirical LEPS surface. The main features discussed are tunneling and threshold behavior for both the ground state and the first excited state of the hydrogen molecule. In the second part, kinetic isotope effects are presented and discussed. Those were calculated in three different ways, using (i) QM transition probabilities, (ii) CL transition probabilities, and (iii) transition state theory (TST-1D). Tunneling coefficients k_QM/k_CL and k_QM/k_TST were calculated and discussed. Finally, a brief comparison with experimental data was performed.