Hidenao Sugawara

A New Constant Deviation Monochromator for Angle Resolved Photoemission Spectroscopy

A new type of constant deviation monochromator equipped with three interchangeable concave gratings (600, 1200 and 2400 grooves/mm) of 2 m radius of curvature was designed and built specifically for angle resolved photoemission spectroscopy at photon energies ranging from 20 to 160 eV. The exit slit of the monochromator is at a fixed position, whereas the entrance slit moves, simultaneously with grating rotation, along the direction of the incident light so as to minimize the amount of defocusing. A monochromatic light spot of 0.5 mm in diamter was obtained at the fixed sample position with the aid of a toroidal postfocussing mirror. It is found over the energy range concerned that the resolution is bettern than 1700 with 25 µm slits, and the photon flux obtained behind the toroidal mirror for a horizontal acceptance angle 0.5 mrad is 4×1010 photons/s when the width of the slits is 50 µm and the stored current for synchrotron radiation is 100 mA.

Front ends for the Photon Factory beam lines

Abstract The front end of each beam line at Photon Factory serves the experimental area with a synchrotron radiation beam of 30 mrad in horizontal aperture. Some specific aspects concerning an acoustic delay line, a fast closing valve, silicon carbide mirrors and a beryllium window assembly installed in the beam lines are presented.

Extreme Ultraviolet Photoemission of MnSi, FeSi and CoSi

The valence band photoemission has been observed on MnSi, FeSi and CoSi over the excitation energy range from 40 to 130 eV. In MnSi, the spectral profile is consistent with the reported energy band calculation. The width of the main band decreases in the order of MnSi, FeSi and CoSi, indicating that the 3 d electrons tend to localize more as the number of the 3 d electrons increases. In FeSi and CoSi, the spectral feature near the Fermi edge is consistent with the existence of a narrow energy gap in the valence-conduction band, although the gap itself is not resolved. In all three materials, no satellite is found. Weak 3 p -3 d resonance is found in the photoemission in each material.

Extreme Ultraviolet Photoemission of CeB6 and PrB6

Photoelectron spectra of CeB 6 and PrB 6 have been measured over the excitation-energy range from 30 to 140 eV. From the locations of the peaks which grow resonantly upon excitation in the giant absorption bands above the 4 d thresholds of rare earths, the binding energies of 4 f electrons in resonance are found to be 2.5 eV in CeB 6 and 4.7 eV in PrB 6 . The shapes of energy distribution curves observed by excitation below resonance agree with the reported energy distribution curve of LaB 6 and with the density-of-states curve calculated on LaB 6 by the Xα-APW method. A sharp peak is resolved at the Fermi edge of CeB 6 . Its origin is discussed in relation to valence fluctuation.

Extreme Ultraviolet Photoelectron Spectra of Manganese Phosphide

The valence band photoelectron spectra of MnP crystals have been measured over the range of excitation energy from 40 to 130 eV using synchrotron radiation. The spectra consist of strong bands ascribable to the Mn 3 d bands and weak structures ascribable to the P 3 s band and the bonding bands of Mn 3 d and P 3 p electrons. Sharp Fermi edge is found in the Mn 3 d band; the consequence is that Mn 3 d electrons are itinerant. The spectral band shape is consistent with the results of energy band calculation reported recently. Resonance enhancement of the photoemission intensity accompanied by the growth of two additional band is found for excitation energies above the threshold of Mn 3 p excitation. The possible origin of this enhancement is discussed.

Extreme ultraviolet photoelectron spectra of alpha manganese

Valence-band photoelectron spectra have been measured for alpha manganese over the range of excitation energy from 30 to 130 eV. The observed spectra show the two-peak structure in agreement with the reported partial density-of-states curve obtained by the tight-binding approximation, although no quantitative agreement is found regarding the peak positions and the width of the band. The 3p-3d resonance is observed at excitation energies above the 3p threshold. A satellite appears at 5.8 eV below the Fermi edge.

Photoelectric Yield Spectra of K-, Rb- and Cs-Halides in the Photon Energy Range 10 to 40 eV

Absolute photoelectric yield spectra of the halides of potassium, rubidium and cesium, and relative yield spectra at various retarding potentials have been measured in the photon energy range from 10 to 40 eV using synchrotron radiation. Prominent minima followed by broad structures which are not found in optical absorption spectra are observed. The absolute values of the yields are high in the region above the minima. Peaks appear at the photon energies corresponding to core-exciton peaks in absorption spectra. These features suggest that electron-electron scattering and the Auger decay of core-excitons occur predominantly in alkali halides. At large retarding potentials, the yield spectra show two broad bands similar to each other. The electronic transitions responsible for their origins will be discussed.

Reflectance spectra of extreme ultraviolet mirrors for synchrotron radiation

Abstract Reflectance spectra have been measured for many materials in the wavelength range from 90 A to 400 A. The angle of incidence ranged from 20° to 85°. The samples were chemical-vapor-deposited silicon carbide (CVD-SiC), a single crystal of silicon with (100) surface, fused quartz, zerodur, pyrex, gold, platinum, copper and two kinds of steel. To obtain reflectances for surfaces for practical use, measurements were made on surfaces sufficiently exposed to air. Reflectances for s-polarized light ( R s ) were measured for all samples. On CVD-SiC, gold and platinum, reflectances for p-polarized light ( R P ) were also observed. At short wavelengths and large angles of incidence, the difference between R s and R P is small, and R P happened to exceed R s in contrast to the result from the Fresnel equation. This may be due to the deviation of the present surfaces of mirrors from an ideal plane. Reflectance spectra of surfaces prepared by some feasible techniques are also presented.

Extreme Ultraviolet Photoemission from Chromium Metal

Photoelectron spectra of chromium metal have been measured in the excitation energy range from 30 to 80 eV at room temperature. Valence band spectra measured at low excitation energies are consistent with that of the calculated density-of-states curve in an overall feature, but not in a detailed feature. Resonant photoemission occurs in the valence band region on excitation above the 3 p threshold. The general features of the intensity variations of valence band structures with excitation energy are consistent with the recent model calculation.

Resonant Photoemission in Transition Metal Bromides

Resonant photoemission in the bromides of Ni, Co, Fe and Mn has been observed for excitations near the 3 p thresholds of the metal ions. Resonance occurs all over the valence band spectra including satellites, and the resonance excitation spectra are similar to those observed in the chlorides. Some features in the main bands shift toward high-binding-energy side upon resonance. This shift gives rise to increase in the crystal field splitting on resonance for NiBr 2 , FeBr 2 and MnBr 2 , but decrease for CoBr 2 ; Racah parameters increase on resonance in all the bromides observed here.