Hannover 2020 – scientific programme
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MO: Fachverband Molekülphysik
MO 17: Theory
MO 17.8: Talk
Thursday, March 12, 2020, 15:45–16:00, f142
On the Molecular Symmetry of Protonated Methane — •Stefan Brackertz1, Benjamin Nukic1, Thomas Salomon1, Per Jensen2, and Stephan Schlemmer1 — 1I. Physikalisches Institut, University of Cologne — 2Physikalische und theoretische Chemie, Universität Wuppertal
The energy term diagram of the lowest energy ro-vibrational states of CH5+ has eluded any analytical description until Schmiedt et al. proposed a 5d superrotor model in 2015. In 2018 Fábri and Császár used quantum graphs to describe the internal motions. Numerical results have been published in 2016 by Wang et al. All of these approaches describe the experimental energies resonably well but seem to be incompatible regarding molecular symmetry.
We present results on the relations between these approaches:
- Schmiedt et al. showed the non-existence of equivalent rotations for the permutations of CH5+ because S5 is not isomorphic to any subgroup of SO(n)×{E,E*} for n < 5. This can also be understood geometrically using the results of Fábri and Császár.
- Fábri and Császár do a splitting of S5=S4×S2 associated with an internal equivalent rotation for the S4 part. This approach gives some clues to the interpretation of the 5d superrotor model.
These considerations are also used for the modeling of a simpler case of a fluxional molecule, He−H3+, which is subject to internal as well as end-over-end rotation.