scholarly journals Conformer-Dependent VUV Photodynamics and Chiral Asymmetries in Pure Enantiomers of Gas Phase Proline

2020 ◽  
Author(s):  
Rim Hadidi ◽  
Dusan Bozanic ◽  
Hassan Ganjitabar ◽  
Gustavo Garcia ◽  
Ivan Powis ◽  
...  
Keyword(s):  
Gas Phase ◽  
Energy Difference ◽  
Molecular Structures ◽  
Theoretical Modelling ◽  
Pyrrolidine Ring ◽  
Conformational Landscape ◽  
Vuv Photoionization ◽  
Molecular Electronic Structure ◽  
Unique Amino Acid ◽  
Structure Calculations

Abstract Proline is a unique amino-acid, with a secondary amine fixed within a pyrrolidine ring providing specific structural properties to proline-rich biopolymers. Gas-phase proline possesses four main H-bond stabilized conformers differing by the ring puckering and carboxylic acid orientation. The latter defines two classes of conformation, whose large ionization energy difference allows a unique conformer-class tagging via electron spectroscopy. Photoelectron circular dichroism (PECD) is an intense chiroptical effect sensitive to molecular structures, hence theorized to be highly conformation-dependent. Here, besides a conformer-dependant cation fragmentation behaviour, we present experimental evidence of an intense and striking conformer-specific PECD, measured in the VUV photoionization of proline. This finding, combined with theoretical modelling, allows a refinement of the conformational landscape and energetic ordering, that proves inaccessible to current molecular electronic structure calculations. Additionally, astrochemical implications regarding a possible link of PECD to the origin of life’s homochirality are considered in terms of plausible temperature constraints.

scholarly journals Conformer-dependent vacuum ultraviolet photodynamics and chiral asymmetries in pure enantiomers of gas phase proline

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Rim Hadidi ◽  
Dušan K. Božanić, ◽  
Hassan Ganjitabar ◽  
Gustavo A. Garcia ◽  
Ivan Powis ◽  
...  
Keyword(s):  
Gas Phase ◽  
Vacuum Ultraviolet ◽  
Energy Difference ◽  
Molecular Structures ◽  
Fragmentation Behavior ◽  
Conformational Landscape ◽  
Vuv Photoionization ◽  
Molecular Electronic Structure ◽  
Unique Amino Acid ◽  
Structure Calculations

AbstractProline is a unique amino-acid, with a secondary amine fixed within a pyrrolidine ring providing specific structural properties to proline-rich biopolymers. Gas-phase proline possesses four main H-bond stabilized conformers differing by the ring puckering and carboxylic acid orientation. The latter defines two classes of conformation, whose large ionization energy difference allows a unique conformer-class tagging via electron spectroscopy. Photoelectron circular dichroism (PECD) is an intense chiroptical effect sensitive to molecular structures, hence theorized to be highly conformation-dependent. Here, we present experimental evidence of an intense and striking conformer-specific PECD, measured in the vacuum ultraviolet (VUV) photoionization of proline, as well as a conformer-dependent cation fragmentation behavior. This finding, combined with theoretical modeling, allows a refinement of the conformational landscape and energetic ordering, that proves inaccessible to current molecular electronic structure calculations. Additionally, astrochemical implications regarding a possible link of PECD to the origin of life’s homochirality are considered in terms of plausible temperature constraints.

Gas-phase electron-diffraction studies of the molecular structures of tetrachlorosulfidotungsten(VI), WSCl4, and tetrachloroselenotungsten(VI), WSeCl4

1982 ◽  
Vol 21 (9) ◽  
pp. 3280-3283 ◽  
Author(s):  
Elizabeth M. Page ◽  
David A. Rice ◽  
Kolbjoern. Hagen ◽  
Lise. Hedberg ◽  
Kenneth. Hedberg
Keyword(s):  
Electron Diffraction ◽  
Gas Phase ◽  
Molecular Structures ◽  
Gas Phase Electron Diffraction

Intrinsic Optical Absorption in Germanium

1964 ◽  
Vol 19 (5) ◽  
pp. 548-552
Author(s):  
Günther Harbeke
Keyword(s):  
Optical Absorption ◽  
Low Temperatures ◽  
Energy Difference ◽  
Direct Absorption ◽  
Band Structure Calculations ◽  
Bulk Single Crystals ◽  
Transmission Measurements ◽  
Absorption Constant ◽  
Valence Bands ◽  
Structure Calculations

The absorption constant of germanium beyond the first direct absorption edge has been determined up to energies of 2.5 eV by transmission measurements on very thin samples prepared from bulk single crystals. The results are discussed in terms of recent band structure calculations and previous reflection measurements. At low temperatures the observed structure gives evidence for exciton formation connected with direct transitions at a saddle point in the energy difference between conduction and valence bands.

Molecular Structures and Compositions oftrans-1,2-Dichlorocyclohexane andtrans-1,2-Difluorocyclohexane in the Gas Phase:  An Electron-Diffraction Investigation

2006 ◽  
Vol 110 (5) ◽  
pp. 2053-2059 ◽  
Author(s):  
Alan D. Richardson ◽  
Kenneth Hedberg ◽  
Karissa Utzat ◽  
Robert K. Bohn ◽  
Jian-Xin Duan ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Gas Phase ◽  
Molecular Structures ◽  
Electron Diffraction Investigation

Computational studies of ice defects

2003 ◽  
Vol 81 (1-2) ◽  
pp. 325-332 ◽  
Author(s):  
P LM Plummer
Keyword(s):  
Defect Formation ◽  
Structural Evolution ◽  
Energy Difference ◽  
Electronic Energy ◽  
Energy Structure ◽  
Defect Site ◽  
And Migration ◽  
Dynamics Simulations ◽  
Small Clusters ◽  
Structure Calculations

Continuing our investigations of the energetics associated with defect formation and migration, both ab initio energy-structure calculations and molecular dynamics simulations are carried out on small clusters of water molecules containing one or more defects in hydrogen bonding. Previous studies in this series have identified structures containing defects that are stable at 0 K or that are transition states between such structures. However, results from this laboratory and elsewhere have shown that the energy required for the production or migration of a defect is more complex than merely the energy difference between the static structures. Cooperative motion of neighbors to the defect site can either increase or decrease the energy involved to produce or annihilate the defect. Thus, experimental measurements associated with the energy of defects in ice can differ substantially from those calculated using static models. By increasing the complexity of the model, the studies described in this report attempt to more realistically simulate a defect-containing ice system. The types of defects studied include ion and ion-pair defects. The initial structures are energetically stable — minima on the electronic energy surface — and contain one or more kinds of defects. Since the means and amount of energy injection can alter the migration path, the energy is introduced into the system in a variety of ways. The structural evolution of the ice system is then monitored as a function of time. PACS Nos.: 82.20Wt, 82.20Kh, 82.30Rs

Sign in / Sign up

Export Citation Format

Share Document