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

Abstract

We present quantitative calculations of the mode‐selective stereomutation tunneling in the chiral hydrogen diselenide isotopomers X2Se2 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 H2O2, HSOH, H2S2, and Cl2S2. 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 D2Se2 are of the same order as the parity‐violating energy difference reported by Laerdahl and Schwerdtfeger (Phys. Rev. A 1999, 60, 4439), whereas for T2Se2 the corresponding tunneling splitting is about three orders of magnitude smaller.

Stereomutation dynamics in hydrogen peroxide

“…We may mention in this context as examples on the one hand hydrogen bond dynamics in isotopomers of hydrogen fluoride dimers [46][47][48][49][50] and inversion in Ammonia isotopomers [51][52][53][54][55] and on the other hand stereomutation dynamics in hydrogen peroxide and related systems [56][57][58][59][60][61][62][63][64]. Hydrogen peroxide in its equilibrium geometry exists in two enantiomeric forms separated by a low torsional barrier (of about 360 cm À1 ) conventionally labelled the P and M enantiomers (see Fig.…”

“…Indeed, hydrogen peroxide has been a prototype molecule for theoretical calculations of molecular parity violating potentials (see [67][68][69][70][71] and the reviews [72,73] for further references). We have discussed the importance of the interplay of parity violation with tunneling dynamics in this context [58][59][60][61][62][63]72,73].…”

Mode-selective stereomutation tunneling and parity violation in HOClH+ and H2Te2 isotopomers

“…The recent theoretical discovery that E pv is predicted to be one to two orders of magnitude larger [21][22][23][24] than anticipated from earlier calculations [18] has given new impetus to the field and the present work contributes to the new effort in this field [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. From both an experimental and theoretical point of view, it would be of interest to study particularly simple prototype molecules or ions.…”

“…The torsional tunneling dynamics were calculated with the quasi-adiabatic channel-reaction path Hamiltonian (RPH) approach described in detail in [27,33,42,43]. Our treatment is a modified version of the RPH approach of Miller et al [59] and is also conceptually related to the adiabatic channel model [60].…”

“…This ion is isoelectronic to HSOH which has been generated in mass spectroscopic experiments [40] and more recently in bulk [41]. This molecule also falls in the general series of axially chiral molecules HXYH, for which we have already presented extensive calculations of parity violation and tunneling in our previous work [21][22][23][24][25][26][27]32,33,42,43]. However, it seems that, so far, parity violation has not been studied for an ionic species of this type.…”