Photoelectron circular dichroism: Chiral asymmetry in the angular distribution of electrons emitted by (+)‐S‐carvone

Abstract

The technique of photoelectron circular dichroism (PECD) is introduced and illustrated by the presentation of results obtained for the C 1s core ionization of (+)-S-carvone enantiomers. Using circularly polarized ionizing radiation, large chiral effects in the angular distribution of photoelectrons emitted from a dilute, randomly oriented gas phase sample can be detected. This effect is predicted in the pure electric dipole approximation and is expected to be quite general. The forward-backward asymmetry regularly exceeds 10%, as demonstrated here for the carbonyl C 1s photoemission of carvone. Calculations are presented that reveal a pronounced dependence of this effect on molecular conformation. In the case of carvone the PECD associated with the C 1s electron localized at the carbonyl group varies with orientation of the isopropenyl tail group at the opposite end of the molecule. Comparisons of calculations with experiment confirm the molecular configuration and permit inferences to be drawn concerning the relative conformer populations in the experimental sample.

Photoelectron circular dichroism of chiral molecules studied with a continuum-state-corrected strong-field approximation

“…The commonly used SFA fails in describing this effect, which leads to the conclusion that not only the orbital from which ionization takes place is important, but also the final scattering state of the emitted electron. This is in accordance with findings in the single-photon PECD, where an asymmetry occurs even with an achiral initial orbital, indicating that the scattering state plays a vital role in the process [39,40]. We have demonstrated that a rather simple approximation for the scattering state is sufficient to yield a nonzero PECD effect and thus to overcome a fundamental limitation of the plain SFA.…”

Detecting chirality in molecules by imaging photoelectron circular dichroism

“…Subsequent experimental work has provided much evidence for such conformational sensitivity to static geometrical structure. [84][85][86][87] Recently, a strong and dramatic dependence on the dynamic variations in nuclear geometry associated with different vibrational modes has been confirmed to be capable of reversing the forward-backward asymmetry. 88 While a good correspondence between calculation and experiment has been achieved for many of the single photon PECD studies, more development is required to extend the possibilities for handling larger molecules and clusters, and to permit capture of more subtle effects associated with electron correlation, etc.…”

Photoelectron Circular Dichroism of Bicyclic Ketones from Multiphoton Ionization with Femtosecond Laser Pulses

“…This may be an additional hint to the importance of the scattering state for this relatively low-kinetic-energy electrons released in the multiphoton process. [68,91,92] For quantification, the same procedure as detailed for camphor has been applied and the results are summarized in Table 3 (LPECD and PPECD derived from Abeltransformed distributions) and Table 4 (Legendre coefficients, Figure 11. Excitation and ionization scheme of the bicyclic ketones fenchone (red), camphor (green) and norcamphor (blue) adapted from Pulm et al [83] The vertical IPs are: camphor: IP: 8.7 eV, [85] fenchone: IP: 8.6 eV, [16] norcamphor: IP: 9.2 eV.…”