Asymmetric photoelectron emission from chiral molecules using a high repetition rate laser

In the chiro-optical phenomenon known as photoelectron circular dichroism, the angular distribution of electrons ionized from chiral molecules by circularly polarized light pulses has been found to be anti-symmetric with respect to the direction of the light propagation. To study this phenomenon, chiral molecules were multiphoton ionized with a femtosecond laser in our laboratory. Using a simple stereo-detection setup, direct measurements of the asymmetry for the exemplar aromatic chiral molecule 1-phenylethanol were made using 260 nm pulses produced at a rate of 1 MHz. It was found that the asymmetry had a linear dependence on Stokes' S₃ parameter indicating that the photoelectron circular dichroism is due to a single photon process from the excited state of the molecule. This is in contrast to previous and new results for camphor where a more complex dependence on S₃ suggested that selective excitation of molecules with certain orientations was influential.