Chiral Torsional Double Wells: Tunneling and Polarizability
Abstract
Quantum tunneling between mirror-related wells of a torsional potential sets the timescale for coherent interconversion of chiral conformers. We ask whether slower tunneling also weakens the transition polarizability in hydrogen peroxide, hydrogen disulfide, and hydrogen diselenide. We use relaxed CCSD(T)//MP2 potentials and a kinetic model that removes overall molecular rotation to obtain the torsional states, then use static polarizabilities to calculate transition matrix elements between them. In the molecular frame used here, symmetry makes the matrix element of the even dipole component vanish between opposite-parity torsional states, while the odd polarizability component has a nonzero matrix element. The two quantities probe different parts of the torsional landscape: tunneling depends on penetration through the barriers, while the polarizability matrix element forms mainly within the wells. Consequently, tunneling slows sharply across the molecular series even as the matrix element grows. Higher torsional doublets and deuterium substitution further show that large changes in tunneling time can occur with little change in the transition polarizability matrix element. Calculated torsional energies for H2O2 and D2O2 agree with experimental values. Thus, slowing coherent interconversion need not weaken the intrinsic transition polarizability.
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BibTeX
@misc{mohtashim2026chiral,
title = {{Chiral Torsional Double Wells: Tunneling and Polarizability}},
author = {Shah Ishmam Mohtashim and Manas Sajjan and Sabre Kais},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.41782},
eprint = {2610.41782},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.41782},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Chiral Torsional Double Wells: Tunneling and Polarizability
AU - Shah Ishmam Mohtashim
AU - Manas Sajjan
AU - Sabre Kais
PY - 2026
DA - 2026/10/30
PB - arXiv
DO - 10.48550/arxiv.2610.41782
UR - https://arxiv.org/abs/2610.41782
AB - Quantum tunneling between mirror-related wells of a torsional potential sets the timescale for coherent interconversion of chiral conformers. We ask whether slower tunneling also weakens the transition polarizability in hydrogen peroxide, hydrogen disulfide, and hydrogen diselenide. We use relaxed CCSD(T)//MP2 potentials and a kinetic model that removes overall molecular rotation to obtain the torsional states, then use static polarizabilities to calculate transition matrix elements between them. In the molecular frame used here, symmetry makes the matrix element of the even dipole component vanish between opposite-parity torsional states, while the odd polarizability component has a nonzero matrix element. The two quantities probe different parts of the torsional landscape: tunneling depends on penetration through the barriers, while the polarizability matrix element forms mainly within the wells. Consequently, tunneling slows sharply across the molecular series even as the matrix element grows. Higher torsional doublets and deuterium substitution further show that large changes in tunneling time can occur with little change in the transition polarizability matrix element. Calculated torsional energies for H_2O_2 and D_2O_2 agree with experimental values. Thus, slowing coherent interconversion need not weaken the intrinsic transition polarizability.
ER -