Photoelectron imaging of XUV photoionization of CO2 by 13-40 eV synchrotron radiation

Valence band photoionization of CO2 has been studied by photoelectron spectroscopy using a velocity map imaging spectrometer and synchrotron radiation. The measured data allow retrieving electronic and vibrational branching ratios, vibrationally resolved asymmetry parameters, and the total electron yield which includes multiple strong resonances. Additionally, the spectrum of low kinetic energy electrons has been studied in the resonant region, and the evolution with photon energy of one of the forbidden transitions present in the slow photoelectrons spectrum has been carefully analyzed, indicating that in the presence of auto-ionizing resonances the vibrational populations of the ion are significantly redistributed

Single quantum dot nanowire LEDs

We report reproducible fabrication of InP-InAsP nanowire light emitting diodes in which electron-hole recombination is restricted to a quantum-dot-sized InAsP section. The nanowire geometry naturally self-aligns the quantum dot with the n-InP and p-InP ends of the wire, making these devices promising candidates for electrically-driven quantum optics experiments. We have investigated the operation of these nano-LEDs with a consistent series of experiments at room temperature and at 10 K, demonstrating the potential of this system for single photon applications

Ultrafast relaxation dynamics of highly-excited states in N2 molecules excited by femtosecond XUV pulses

We used velocity-map-imaging to measure electronic and nuclear dynamics in N2 molecules excited by a train of attosecond pulses. A time-to-space mapping of autoionization channel is demonstrated. It is found that the autoionization becomes energetically allowed when the two nuclei are still very close (~ 3 Å) and that it can be coherently manipulated by a strong femtosecond infrared pulse. © Owned by the authors, published by EDP Sciences, 2013

Molecular Movies from Molecular Frame Photoelectron Angular Distribution (MF-PAD) Measurements

We discuss recent and on-going experiments, where molecular frame photoelectron angular distributions (MFPADs) of high kinetic energy photoelectrons are measured in order to determine the time evolution of molecular structures in the course of a photochemical event. These experiments include, on the one hand, measurements where single XUV/X-ray photons, obtained from a free electron laser (FEL) or by means of high-harmonic generation (HHG), are used to eject a high energy photoelectron, and, on the other hand, measurements where a large number of mid-infrared photons are absorbed in the course of strong-field ionization. In the former case, first results indicate a manifestation of the both the electronic orbital and the molecular structure in the angle-resolved photoelectron distributions, while in the latter case novel holographic structures are measured that suggest that both the molecular structure and ultrafast electronic rearrangement processes can be studied with a time-resolution that reaches down into the attosecond and few-femtosecond domain