Isotope and vibrational excitation effects in ultracold chemical reactions

We discuss the effect of vibrational excitation on chemical reaction between O($^1D$) and H$_2$ and OH+O at cold and ultracold temperatures. The effect of isotope substitution is investigated by exploring dynamics of O($^1D$)+D$_2$ reaction and comparing results against its H$_2$ counterpart. It is found that while vibrational excitation has a moderate effect on OH+O reaction, it has only marginal effect on O($^1D$)+H$_2$/D$_2$ reactions. For $v=2$ and $v=3$ of OH it is found that non-reactive relaxation pathway is dominated by a multi quantum process than a sequential single quantum pathway. Kinetic isotope effect is determined for the O($^1D$)+H$_2$/D$_2$ systems as the ratio of rate coefficients for H$_2$ and D$_2$ reactions and comparisons are made with available room temperature experimental data.