Rotational Effects on Radiationless Transition IV: Hyperfine Interaction and Deuterium Isotope Effects

This is the authors' abstract. We don't add key points for this paper.

The theory of the rotational effects on radiationless transitions in typical azines is extended to include the hyperfine (hf) interaction term, while examining their deuterium (isotope) effects on the decay behaviors after excitation into the rotational levels belonging to their S10 levels, i.e. their ground vibrational levels of S1 states. The Fermi-contact hf term is shown to be enough to endorse the coupling between rotational levels that are different either in symmetries or in some angular-momentum quantum numbers. The deuterium (D) effect is found to be not simply described as a conventional isotope effect: Changes by D substitution are brought about in densities of triplet states and hf coupling terms, as well as molecular symmetry groups. While interpreting the experimental data, modifications of the schemes are made from those presented earlier in this series.