The angle-resolved inner-shell photoionization of R-trifluoromethyloxirane, C3H3F3O, is studied experimentally and theoretically. Thereby, we investigate the photoelectron circular dichroism (PECD) for nearly-symmetric O 1s and F 1s electronic orbitals, which are localized on different molecular sites. The respective dichroic β1 and angular distribution β2 parameters are measured at the photoelectron kinetic energies from 1 to 16 eV by using variably polarized synchrotron radiation and velocity map imaging spectroscopy. The present experimental results are in good agreement with the outcome of ab initio electronic structure calculations. We report a sizable chiral asymmetry β1 of up to about 9% for the K-shell photoionization of oxygen atom. For the individual fluorine atoms, the present calculations predict asymmetries of similar size. However, being averaged over all fluorine atoms, it drops down to about 2%, as also observed in the present experiment. Our study demonstrates a strong emitter-and site-sensitivity of PECD in the one-photon inner-shell ionization of this chiral molecule.

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A time-resolving and energy-dispersive photoelectron detector for time-resolved experiments has been set up for pump–multiple-probe experiments with combined laser and synchrotron radiation. The time resolution of the detector of about 1 ns allows an assignment of the photoelectron signal to a specific synchrotron radiation pulse for any filling pattern of third-generation synchrotron storage rings. This leads to an overall temporal resolution given by the synchrotron radiation pulse width, which is 30 ps at the synchrotron radiation facility BESSY, Berlin. Application of the pump–multiple-probe technique is demonstrated for time-resolved photoemission experiments with combined laser and synchrotron radiation.

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