Photoelectron circular dichroism refers to the forward/backward asymmetry in the photoelectron angular distribution with respect to the propagation axis of circularly polarized light. It has recently been demonstrated in femtosecond multi-photon photoionization experiments with randomly oriented camphor and fenchone molecules [C. Lux et al., Angew. Chem. Int. Ed. 51, 5001 (2012); C. S. Lehmann et al., J. Chem. Phys. 139, 234307 (2013)]. A theoretical framework describing this process as (2+1) resonantly enhanced multi-photon ionization is constructed, which consists of twophoton photoselection from randomly oriented molecules and successive one-photon ionisation of the photoselected molecules. It combines perturbation theory for the light-matter interaction with ab initio calculations for the two-photon absorption and a single-center expansion of the photoelectron wavefunction in terms of hydrogenic continuum functions. It is verified that the model correctly reproduces the basic symmetry behavior expected under exchange of handedness and light helicity. When applied it to fenchone and camphor, semi-quantitative agreement with the experimental data is found, for which a sufficient d wave character of the electronically excited intermediate state is crucial.

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An extended theoretical analysis of the photodissociation of the smallest Criegee intermediate \ce{CH_2OO} following excitation to the B state is presented. It relies on explicitly correlated multireference electronic wavefunctions combined...

The spectroscopy of the four-carbon Criegee intermediate, methyl vinyl ketone oxide (MVK-oxide), following UV excitation to the B state (corresponding to the first $\pi^* \leftarrow \pi$ electronic transition) is studied theoretically, relied on single reference electronic wave function and a quantum dynamical approach for the nuclear motion. Two interacting electronic states $B{}^1\rm{A'}$ and $C{}^1\rm{A'}$ together with two nuclear degrees of freedom (\ce{O-O} stretching and \ce{C-O-O} bending modes) are considered in the dynamical approach. The computed absorption spectrum is found to agree well with the available experimental recordings. The existence of the weak oscillatory structures in the absorption spectrum are argued likely due to the fact that the excitation energy range of the first $\pi^* \leftarrow \pi$ electronic transition is below the energy barrier of the diabatic B state ($\sim 215$~nm) and thus below the sufficiently deep well occurring at the intermediate \ce{O-O} distances. Thissuggests the recurrences of the wavepacket, which might be considered as origin of the weak oscillatory structures in the absorption spectrum. The computed electronic excitation profile of MVK-oxide is predicted to peak at $373$ nm.

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