Fourfold Differential Photoelectron Circular Dichroism.

We report on a joint experimental and theoretical study of photoelectron circular dichroism (PECD) in methyloxirane. By detecting O 1s photoelectrons in coincidence with fragment ions, we deduce the molecule's orientation and photoelectron emission direction in the laboratory frame. Thereby, we retrieve a fourfold differential PECD clearly beyond 50%. This strong chiral asymmetry is reproduced by ab initio electronic structure calculations. Providing such a pronounced contrast makes PECD of fixed-in-space chiral molecules an even more sensitive tool for chiral recognition in the gas phase.

Determination of Mean Cluster Sizes by Fluorescence Detection upon Site-Specific Photoexcitation.

Electronic excitations in the valence shell of Ne clusters were studied by fluorescence spectroscopy. The measured fluorescence excitation functions contain information about the nature and number of excitonic states and the mean cluster size of the produced size distribution. Mean cluster sizes were determined by comparing surface and bulk contributions using a multidimensional fitting algorithm, with good agreement to commonly used scaling laws. The influence of different size distributions, which were not considered in previous investigations, on homogeneous noble gas cluster jets is implemented in the proposed model. The present work is the first approach using fluorescence spectroscopy for the determination of the mean size of Ne cluster jets created by supersonic expansion.

Optimised XUV holography using spatially shaped high harmonic beams.

We present a novel method for controlling the transverse positions and relative powers of multiple high-order harmonic beams. A phase-only spatial light modulator is used to produce multiple infrared foci, the positions and intensities of which can be controlled programmably, enabling the generation and control of multiple HHG beams. To demonstrate the utility of this method we perform Fourier transform holography with separate illumination of the object and reference pinhole by a pair of HHG beams, which makes optimal use of the available photon flux. The programmable control of the spatial distribution of HHG beams demonstrated here offers new opportunities for experiments at extreme ultraviolet (XUV) wavelengths, particularly for photon intensive applications such as imaging.

Erratum: Electron Localization in Dissociating H_{2}

This corrects the article DOI: 10.1103/PhysRevLett.116.043001.

Electron Localization in Dissociating H_{2}

We investigate the dissociation of H_{2}^{+} into a proton and a H^{0} after single ionization with photons of an energy close to the threshold. We find that the p^{+} and the H^{0} do not emerge symmetrically in the case of the H_{2}^{+} dissociating along the 1sσ_{g} ground state. Instead, a preference for the ejection of the p^{+} in the direction of the escaping photoelectron can be observed. This symmetry breaking is strongest for very small electron energies. Our experiment is consistent with a recent prediction by Serov and Kheifets [Phys. Rev. A 89, 031402 (2014)]. In their model, which treats the photoelectron classically, the symmetry breaking is induced by the retroaction of the long-range Coulomb potential onto the dissociating H_{2}^{+}.

Evolution of interatomic Coulombic decay in the time domain.

During the past 15 years a novel decay mechanism of excited atoms has been discovered and investigated. This so-called interatomic Coulombic decay (ICD) involves the chemical environment of the electronically excited atom: the excitation energy is transferred (in many cases over long distances) to a neighbor of the initially excited particle usually ionizing that neighbor. It turned out that ICD is a very common decay route in nature as it occurs across van der Waals and hydrogen bonds. The time evolution of ICD is predicted to be highly complex, as its efficiency strongly depends on the distance of the atoms involved and this distance typically changes during the decay. Here we present the first direct measurement of the temporal evolution of ICD using a novel experimental approach.

Vibrationally resolved decay width of interatomic Coulombic decay in HeNe.

We investigate the ionization of HeNe from below the He 1s3p excitation to the He ionization threshold. We observe HeNe+ ions with an enhancement by more than a factor of 60 when the He side couples resonantly to the radiation field. These ions are an experimental proof of a two-center resonant photoionization mechanism predicted by Najjari et al. [Phys. Rev. Lett. 105, 153002 (2010)]. Furthermore, our data provide electronic and vibrational state resolved decay widths of interatomic Coulombic decay in HeNe dimers. We find that the interatomic Coulombic decay lifetime strongly increases with increasing vibrational state.