Vibrationally resolved molecular-frame angular distribution of O 1s photoelectrons from CO2 molecules

Vibrationally resolved O 1s photoelectron angular distributions from CO2 molecules, aligned parallel and perpendicular to the electric vector of the incident light, have been measured in the 5 sigma(g)(*) shape resonance region, with photon energies up to 2 eV above the O 1s ionization threshold, using multiple-coincidence electron-ion momentum imaging spectroscopy. The angular distributions depend on the vibrational quanta of the antisymmetric vibrations in the O 1s ionized state but do not vary significantly as a function of the photon energy across the 5 sigma(g)(*) shape resonance

Electron transfer during the dissociation of CH3F+ produced by resonant photoemission following F 1s excitation

We present experimental evidence for pronounced electron transfer from C to F(+) happening during the breakup of CH(3)F(+) ions in gas phase produced by resonant photoemission following F 1s -> 6a(1)(*) core excitation of CH(3)F. We measured the momentum of the ionic fragments in coincidence with the F KVV Auger electrons that show a Doppler shift reflecting the motion of the F nucleus. The correlation between Doppler shift and ion momentum is opposite for the F(+) and the CH(2)(+) fragments, indicating that CH(2)(+) is produced by electron transfer from C to F(+), after the Auger electron emission from excited moving F. This finding is rationalized by calculations of the potential energy curves of the main states involved in the excitation and decay processes

Site-specific fragmentation following F 1s photoionization of free CF3SF5 molecules studied by electron-ion coincidence spectroscopy

We have studied site-specific fragmentation caused by F 1s photoionization of free CF3SF5 molecules. Energy-resolved electrons and mass-resolved ions were detected in coincidence. We found an enhancement of the CF3+ion production in coincidence with photoelec-trons emitted from F atoms in the SF5 group due to a reaction path leading to CF3+–SF+ pair production. We found an enhancement of the CF+ and C+ ions due to F 1s electron emission from the CF3 group. Site-selectivity was also observed for the CF+–SF+ ,CF+ –SF2+ ;CF+ –SF3+ , C+ –F+ , C+ –S+ and C+ –SF+ ion pair production

Dissociative double ionization of formic acid in intense laser fields

We have investigated dissociative double ionization of formic acid by intense 100 fs laser pulses at 800 nm, using ion-ion coincidence momentum spectroscopy. Neither changing the laser power nor switching the laser polarization from linear to circular affected energy distributions of the ion pair. This observation is interpreted as implying the occurrence of sequential enhanced ionization. (C) 2010 Elsevier B.V. All rights reserved

Young's double-slit experiment using two-center core-level photoemission: Photoelectron recoil effects

Core-level photoemission from N-2 can be considered an analogue of Young's double-slit experiment (YDSE) in which the double-slit is replaced by a pair of N 1s orbitals. The measured ratio between the 1 sigma(g) and 1 sigma(u) photoionization cross-sections oscillates as a function of photoelectron momentum, due to two-center YDSE interference, exhibiting a remarkable dependence on the vibrational sub-levels of the core ionized state. We theoretically demonstrate that the recoil of the photoelectron given to the ionized N atom strongly influences this interference pattern. The reason for this is that the momentum transfer affects the phases of the photoionization amplitudes. (c) 2007 Published by Elsevier B.