Decoupling vibration and electron energy dependencies in the photoelectron circular dichroism of a terpene, 3-carene

Ganjitabar, Hassan; Garcia, Gustavo; Nahon, Laurent; Powis, Ivan

Abstract

A fresh perspective on the interaction of electron and nuclear motions in photon induced dynamical processes can be provided by the coupling of photoelectron angular distributions and cation vibrational states in the photoionization of chiral molecules using circularly polarized radiation. The chiral contributions, manifesting as a forward-backward asymmetry in the photoemission, can be assessed using Photoelectron Circular Dichroism (PECD), which has revealed an enhanced vibrational influence exerted on the outgoing photoelectron. In this paper, we investigate the PECD of a rigid chiral monoterpene, 3-carene, using single-photon vacuum ultraviolet ionization by polarized synchrotron radiation and selecting energies from the ionization threshold up to 19.0 eV. By judicious choice of these photon energies, two factors that influence PECD asymmetry values, electron kinetic energy and ion vibrational level, can be effectively isolated, allowing a clear demonstration of the very marked vibrational effects. A slow photoelectron spectrum is used to examine the vibrational structure of the isolated outermost valence (HOMO) photoelectron band, and peak assignments are made with the aid of a Franck-Condon simulation. Together, these provide an estimate of the adiabatic ionization energy as 8.385 eV. The reported chiral asymmetry from the randomly oriented 3-carene enantiomers reaches a maximum of over 21%. Theoretical PECD calculations, made both for the fixed equilibrium molecular geometry and also modeling selected normal mode vibration effects, are presented to provide further insight.

Citation

Ganjitabar, H., Garcia, G., Nahon, L., & Powis, I. (2020). Decoupling vibration and electron energy dependencies in the photoelectron circular dichroism of a terpene, 3-carene. Journal of Chemical Physics, 153(3), Article 034302. https://doi.org/10.1063/5.0013448

• Journal Article Type: Article
• Acceptance Date: Jun 18, 2020
• Online Publication Date: Jul 16, 2020
• Publication Date: Jul 21, 2020
• Deposit Date: Jul 6, 2020
• Publicly Available Date: Jul 16, 2020
• Journal: Journal of Chemical Physics
• Print ISSN: 0021-9606
• Electronic ISSN: 1089-7690
• Publisher: American Institute of Physics
• Peer Reviewed: Peer Reviewed
• Volume: 153
• Issue: 3
• Article Number: 034302
• DOI: https://doi.org/10.1063/5.0013448
• Public URL: https://nottingham-repository.worktribe.com/output/4753080
• Publisher URL: https://aip.scitation.org/doi/10.1063/5.0013448
• Additional Information: This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Ganjitabar, H., Garcia, G., Nahon, L., & Powis, I. (2020). Decoupling vibration and electron energy dependencies in the photoelectron circular dichroism of a terpene, 3-carene. Journal of Chemical Physics, 153(3), https://doi.org/10.1063/5.0013448 and may be found at https://aip.scitation.org/doi/10.1063/5.0013448.