Mode‐selective stereomutation tunneling as compared to parity violation in hydrogen diselenide isotopomers ^1,2,3H₂⁸⁰Se₂

Abstract

Abstract We present quantitative calculations of the mode‐selective stereomutation tunneling in the chiral hydrogen diselenide isotopomers X 2 Se 2 with X = H, D, and T. The torsional tunneling stereomutation dynamics were investigated with a quasi‐adiabatic channel quasi‐harmonic reaction path Hamiltonian approach, which treats the torsional motion anharmonically in detail and all remaining coordinates as harmonic (but anharmonically coupled to the reaction coordinate). We also investigated the influence of the excitation of fundamental modes on the stereomutation dynamics and predict which modes should be promoting or inhibiting. Our stereomutation dynamics results and the influence of parity violation on these are discussed in relation to our recent investigations for the analogous molecules H 2 O 2 , HSOH, H 2 S 2 , and Cl 2 S 2 . The electronic potential energy barrier heights for the torsional motion of hydrogen diselenide are similar to those of HSOH, whereas the torsional tunneling splittings are similar to the corresponding values of HSSH. The ground‐state torsional tunneling splittings calculated here for D 2 Se 2 are of the same order as the parity‐violating energy difference reported by Laerdahl and Schwerdtfeger ( Phys. Rev. A 1999, 60 , 4439), whereas for T 2 Se 2 the corresponding tunneling splitting is about three orders of magnitude smaller.