H. Iwayama

A local chemical environment effect in site-specific Auger spectra of ethyl trifluoroacetate

We have investigated a local chemical environment effect on Auger spectra of ethyl trifluoroacetate (C(4)H(5)F(3)O(2)), using multi-electron coincidence spectroscopy and high-resolution electron spectroscopy. Site-specific KVV Auger spectra for each carbon atom, and for the fluorine and oxygen atoms are presented. The extent of hole localization in the final dicationic states was investigated with the help of theoretical calculations based on a two-hole population analysis. The Auger spectra have been simulated using a statistical approach. It is found that all Auger decays populate mainly localized dicationic states, with the two holes located either on the same fluorine atom or on adjacent fluorine atoms. While the decay of the F 1s hole populates exclusively the former states, the latter class of states is also populated by the decay of the C and O 1s holes.

Observation of an optical vortex beam from a helical undulator in the XUV region

The observation of an optical vortex beam at 60u2005nm wavelength, produced as the second-harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam. The experimental results were well reproduced by simulation.

Stability and dissociation dynamics of N2++ ions following core ionization studied by an Auger-electron–photoion coincidence method

An Auger-electron-photoion coincidence (AEPICO) method has been applied to study the stability and dissociation dynamics of dicationic states after the N K-shell photoionization of nitrogen molecules. From time-of-flight and kinetic energy analyses of the product ions, we have obtained coincident Auger spectra associated with metastable states of N2 (++) ions and dissociative states leading to N2 (++) → N(+) + N(+) and N(++) + N. To investigate the production of dissociative states, we present two-dimensional AEPICO maps which reveal the correlations between the binding energies of the Auger final states and the ion kinetic energy release. These correlations have been used to determine the dissociation limits of individual Auger final states.

Stability of Auger final dicationic states of core-ionized N2 molecules studied by Auger-electron ion coincidence measurements

We present experimental results for AEPICO measurements following core photoionization of N2 molecules, with using an AEPICO spectrometer in which a toroidal electron energy analyzer and an ion momentum spectrometer are installed.

Photo-induced ultrafast dissociation following deep-core-electron excitation

Creation of deep core holes leads to extensive nuclear dynamics on a few femtosecond timescale despite the very short (τ ≤ 1 fs) lifetime of such states. This is because the 1st steps of the relaxation processes (i.e. both radiative and non-radiative decays) generate intermediate states with one and multiple holes in core orbitals. As an example, ultrafast dissociation is observed in three well-distinguishable LVV Auger decay channels for HCl following Cl1s→σ* excitation.

Photon-in, Photon-Out Gas-Phase Experiments at the SPring-8 Compact SASE Source SCSS

The study of the interaction of electromagnetic radiation with matter is currently undergoing a revolution with the advent of coherent, intense, ultrafast radiation sources at short wavelengths. In the extreme ultraviolet (EUV) to soft X-ray wavelength region sources based on high-harmonic generation can provide attosecond pulses, and in the soft X-ray to hard X-ray region free electron lasers provide unprecedented intensities of coherent radiation. In this article we describe some gas phase fluorescence spectroscopy experiments performed using the SPring-8 compact SASE source [1], which was originally constructed as a test facility for the SPring-8 Angstrom compact free electron laser SACLA [2].

Site-specific Auger electron spectra of ethyl trifluoroacelate molecules studied by magnetic bottle electron spectrometer

We performed multielectron coincidence measurements for inner-shell photoionizations of ethyl trifluoroacelate molecules (C4H5F3O2) using a magnetic bottle electron spectrometer. From a two dimensional coincidence map between a photoelectron and Auger electron for C 1s ionizations, we extracted site-specific Auger electron spectra for each carbon site and corresponding binding energy of doubly charged states.