The kinetic-energy release distributions (KERDs) of the fragment ion pairs (O++CO+ and C++O+) produced in dissociative double photoionization of carbon dioxide have been determined by analyzing the photoion–photoion coincidence spectra measured in the region hν=40–100 eV by use of a time-of-flight mass spectrometer and synchrotron radiation. The mechanism of the three-body dissociation (CO2+2→C++O++O) has been examined to take place sequentially via CO+ by a triple photoelectron–photoion–photoion coincidence experiment. The KERD observed for the O++CO+ and C++O+ channels at low excitation energies cannot be explained by a simple framework whereby a doubly charged molecular ion (AB2+) is directly produced on single photon absorption followed by the dissociation of AB2+ into two ionic fragments. Some of the ion pairs are produced through indirect processes in which highly excited CO2*+ and CO2** (double Rydberg) states converging to the high-lying CO2+2 electronic states autoionize before and after dissociation. From the observed KERDs for the O++CO+ and C++O+ channels of CO2+2, the range of the intercharge distances of two positive holes is estimated by assuming that the KER is given purely by Coulomb repulsion.

A novel variably polarized angle-resolved photoemission spectroscopy beamline in the vacuum-ultraviolet (VUV) region has been installed at the UVSOR-II 750 MeV synchrotron light source. The beamline is equipped with a 3 m long APPLE-II type undulator with horizontally/vertically linear and right/left circular polarizations, a 10 m Wadsworth type monochromator covering a photon energy range of 6-43 eV, and a 200 mm radius hemispherical photoelectron analyzer with an electron lens of a +/-18 degrees acceptance angle. Due to the low emittance of the UVSOR-II storage ring, the light source is regarded as an entrance slit, and the undulator light is directly led to a grating by two plane mirrors in the monochromator while maintaining a balance between high-energy resolution and high photon flux. The energy resolving power (hnu/Deltahnu) and photon flux of the monochromator are typically 1 x 10(4) and 10(12) photons/s, respectively, with a 100 microm exit slit. The beamline is used for angle-resolved photoemission spectroscopy with an energy resolution of a few meV covering the UV-to-VUV energy range.

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Photoelectron spectroscopy resolved in three-dimensional momentum space with a microscopic field of view is realized by combining a so-called Momentum Microscope with a soft X-ray synchrotron radiation source. A new experimental station for momentum-resolved photoelectron micro-spectroscopy and spectro-microscopy has been built at BL6U, an undulator-based soft X-ray beamline of the UVSOR synchrotron facility. This experimental station specializes in characterizing the electronic structure of surface atomic sites, thin films, molecular adsorbates, and bulk crystals. The instrument details are described along with possible measurement techniques.