Photoelectron Circular Dichroism in Chiral Molecules

Determination of accurate electron chiral asymmetries in fenchone and camphor in the VUV range: sensitivity to isomerism and enantiomeric purity

“…With caveats discussed above, b1 is very well reproduced by the CMS--Xα modeling. In a more general context the enhanced sensitivity of the chiral parameter b1 to the molecular potential-and thus to effects such as isomerism, chemical substitution, conformers, vibrational dynamics, clustering-has been discussed previously 3,6,7 and arises from the strong dependence on the phase shifts of the different outgoing partial waves that interfere in the scattering process 5 . This dependency has been shown to be much more marked in the dichroic parameter b1 than in the anisotropy parameter β or in the cross section 16 , so that tiny changes in the molecular potential will have a much larger effect on this new observable (b1) accessible on randomly--oriented chiral targets.…”

“…However, unlike the usual cross section σ or the asymmetry parameter β, this new observable has a pure quantum origin in the scattering of the outgoing electron by an intrinsically chiral potential, being also fully dependent on the sine of the relative phase between adjacent outgoing partial wave continuum functions 5 . This phase dependence makes b1 a very sensitive probe of the whole molecular potential, much more so than σ or β, with a demonstrated dependence on conformers 11--15 , chemical substitution 16,17 , dimerization 18 and clustering 19,20 , and even vibrational--dynamics 21,22 .…”

The Interplay Between Conformation and Absolute Configuration in Chiral Electron Dynamics of Small Diols

“…The chiral electron dynamics observed in PECD generally derive from both the initial state (orbital), and a final state scattering of the outgoing electron off the chiral molecular potential. [5] A reasonable inference is that in the 13BD calculated PECD, conformation induced, pseudo-enantiomerism of the initially highly localized HOMO provokes the dominant sensed chirality but that this is effectively suppressed by an enhanced influence of configurational chirality at energies around the shape resonance. At the same time fixed geometry calculations such as these are known to overemphasize such resonant effects.…”

“…[4] Here we examine exhibited chirality using photoelectron circular dichroism (PECD). A particular advantage over other chiroptical measures is that PECD provides an orbitally selective probe of molecular chirality, [5][6][7] allowing specific focus to be given to responses of the HOMO frontier orbital. Specifically, PECD isolates and extracts the phenomenological coefficient, 1 {+1} , of an odd cos term in the photoelectron angular distribution (See Supporting Information and Refs [5,6] ) which can then directly express the chiral asymmetry observed in the forward-backward ( = 0, ) directions as a Kuhn asymmetry factor, = 2 1 {+1} .…”

“…Specifically, PECD isolates and extracts the phenomenological coefficient, 1 {+1} , of an odd cos term in the photoelectron angular distribution (See Supporting Information and Refs [5,6] ) which can then directly express the chiral asymmetry observed in the forward-backward ( = 0, ) directions as a Kuhn asymmetry factor, = 2 1 {+1} . From a theoretical perspective for interpretation, the 1 {+1} parameter embodies the dynamics of the mobile electron [5] as it is ejected from the selected orbital and moves out through the chiral potential of the molecular framework.…”