Kazutoshi Fukui

A plane-grating monochromator for 2 eV ≤ hv ≤ 150 eV

Abstract Design and performance of a plane-grating monochromator at UVSOR facility are described. Two monochromators of the present design have been constructed and are used for optical and photoelectron spectroscopy of solids.

Decay time measurements of intrinsic luminescence in alkali halides using single-bunched light pulses from UVSOR

The combination of single-bunched light pulses (duration: 0.5 ns, interval: 177.6 ns) from UVSOR (Okazaki, Japan) with a method of time-correlated single-photon counting was applied to study decay behaviors of intrinsic luminescence in nine typical alkali halide crystals (Na, K, Rb) × (Cl, Br, I). Under excitation into the band-to-band transition, two emission bands, so far called σ emission (fluorescence with a short lifetime) and π emission (phosphorescence with a much longer lifetime), were observed in general at LHeT. The decay behaviors observed were essentially the same as those reported in previous studies where pulsed particles were used as an excitation source. A novel situation has, however, been recognized in the π emission in both NaBr and NaI: A fluorescent component was found clearly to coexist with the long-lived phosphorescent component. This suggests that the initial state of the π emission in NaBr and NaI is a singlet-triplet pair slightly split by the exchange interaction.

Constant deviation monochromator for the range 100 Å≤λ≤1000 Å

A grazing incidence constant deviation monochromator with a spherical concave grating was fabricated for use with undulator radiation. It has a simple scanning mechanism with fixed entrance and exit slits, as well as fixed directions of incident and exit beams. It has been installed into an undulator beamline at IMS. Synchrotron radiation from a bending section also can be introduced into the monochromator by using premirrors. The energy resolution of the monochromator is better than 70 meV at the photon energy of 94 eV with 10‐μm slits, when the bending magnet synchrotron radiation is used. The spot size of the zeroth‐order light is 1.5(v)×2.0(h) mm2 at the distance of 1.85 m behind a postmirror. The photon flux of the undulator radiation behind the exit slit is approximately 1×1012 photons/s at the peak, when both the entrance and exit slits are 100 μm (ΔE=0.08 eV) and the stored current is 50 mA.

Reconstruction of BL7B for UV, VIS and IR spectroscopy with a 3 m normal-incidence monochromator

The beamline BL7B at the UVSOR facility for solid-state spectroscopy is currently under reconstruction. This reconstruction mainly involves the replacement of the 1 m Seya-Namioka-type monochromator (50-600 nm) with a 3 m NIM (modified version of McPherson model 2253), which covers the 50-1000 nm range with three gratings. The deviation angle of the gratings is 15 degrees. For linear and circular polarization experiments, the beamline optics consist of a two-grazing-incidence (87.5 degrees ) pre-mirror system and a normal-incidence (15 degrees ) post-mirror.

Optical properties of nanocrystalline FeSi2 and the effects of hydrogenation

Various optical measurements confirm that optical absorption in uniform thin films made from nanocrystalline iron disilicide (nc-FeSi2) with a 3–5nm radius is larger by about 10% than that of single crystalline β-FeSi2. It is also found that the hydrogenation of nc-FeSi2 changes strongly its optical characteristic energies. The nanocrystalline state appears characteristically in the imaginary part of dielectric constants of β-FeSi2 around 2–3eV.

Photogenerated Carriers in SrTiO3 Probed by Mid-Infrared Absorption

Infrared absorption spectra of SrTiO 3 have been measured under above-band-gap photoexcitations to study the properties of photogenerated carriers, which should play important roles in previously reported photoinduced phenomena in SrTiO 3 . A broad absorption band appears over the entire mid-infrared region under photoexcitation, which is attributed to absorption by the photogenerated carriers occupying in-gap states. The photoinduced absorption is strongly dependent on temperature even below 35 K, where the average photocarrier density is nearly constant. The data show that the density of in-gap states occupied by the photocarriers is high and distributed over a wide energy range extending to the band edges.

Optical Spectra of Cadmium Halide Crystals in 3–30 eV Region

Reflection spectra of single crystals of CdCl 2 , CdBr 2 and CdI 2 at 35 K were measured in the region up to 30 eV using synchrotron radiation. Photoemission experiments were also performed on in-situ evaporated films of cadmium halides to determine binding energies of the outermost s -core levels of halogen ions. Optical constants were derived through Kramers-Kronig analysis. In the region up to 15 eV were found a number of peaks which are attributed to the transitions from the halogen valence band to the cadmium 5 s and 5 p conduction bands. Around 16 eV were observed the peaks due to the Cd 4 d core excitons. Weak structures in the 19-24 eV region are assigned to the transitions from the halogen s -core levels. In CdI 2 , it was found that the total oscillator strength for the transition from the valence band is enhanced due to the presence of shallow core levels.

A plane‐grating monochromator for radiometric calibration

A new plane‐grating monochromator and calibration chamber were constructed for the radiometric calibration of plasma diagnostic devices. The monochromator is designed to cover a wavelength range of 1.8–238 nm with moderate resolving power of 500±200 in λ/Δλ. To check the performance of the monochromator, spectral distribution and resolution were measured by experiments on photoemission from solids and photoionization of rare gases. The characterization of multilayer reflectors by the use of this beamline is demonstrated.

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm−1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.

Front end and optics of infrared beamline at SPring-8

Abstract An infrared (IR) beamline, BL43IR, at SPring-8 has been constructed for IR spectroscopies under extreme conditions. The beamline covers a very wide photon energy range in the IR region and offers a brilliant IR photon beam to the experimental end stations. The IR light from SPring-8 is collected by a newly designed optical system including a so-called “magic mirror”. The design of the optical system and the obtained results are reported.