Powis Ivan
School of Chemistry, The University of Nottingham, University Park, Nottingham, United Kingdom.
Chirality. 2008 Sep;20(9):961-8. doi: 10.1002/chir.20537.
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.
介绍了光电子圆二色性（PECD）技术，并通过展示（+）-S-香芹酮对映体C 1s 内层电离所获得的结果进行说明。使用圆偏振电离辐射，可以检测到从稀薄、随机取向的气相样品发射的光电子角分布中的大手性效应。这种效应在纯电偶极近似中是可以预测的，并且预计是相当普遍的。如本文所示，香芹酮羰基C 1s光发射的前后不对称性通常超过10%。计算结果表明，这种效应明显依赖于分子构象。就香芹酮而言，与羰基处C 1s电子相关的PECD随分子另一端异丙烯基尾基团的取向而变化。计算结果与实验结果的比较证实了分子构型，并允许推断实验样品中相对构象体的数量。
