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Energy distribution curves of valence-band photoelectrons in CeCu 2 Si 2 excited with photons at low energies coincide well with the energy-band density of states curve. The 4 f partial energy distribution curve estimated as the difference between the on- and off-resonance spectra in the 4 d –4 f resonant photoemission has a broad profile extending up to 8 eV with three weak features at 0.4, 1.5 and 2.5 eV and does not resemble the 4 f partial density of states curve given by the energy band calculation. The overall shape of the 4 f partial energy distribution curve in the major part below 4 eV is similar to a 4 f spectrum calculated by Gunnarsson-Schonhammer on the basis of the Anderson model.

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.

The optical conductivities of K–Rb and K–Cs alloys have been measured at liquid nitrogen temperature using synchrotron radiation from a 0.4 GeV electron storage ring over the photon energy range from 10 to 30 eV. The spectra of the alloys have the profiles given by the proportional sums of the spectra of pure alkali metals and this feature suggests the localization of the excitation of outer-most p -shell electrons. The critical exponent of the Fermi edge singularity is altered by alloying. Its concentration-dependence is interpreted as indicating that the shape of spikes at the edge is affected not by the density of states but by the size of the core hole. The energy positions of the edge are shifted by alloying. The amount of the shift is dependent on the concentration and increases for increasing atomic number. This, along with the change in the exponent, may be ascribed to charge transfer effects due to alloying.

The status of photoabsorption and photoreflection spectroscopy of solids, especially transition metal and rare earth compounds, is reviewed along with the difficulties inherent to current models used for their interpretation. The importance of sample preparation and characterization in this area of solid state research - and technology — illustrated.

Synchrotron radiation monochromatized at energies 76, 61, and 40 eV has been used to obtain the photoemission spectra of valence electrons in Ni${\mathrm{Cl}}_{2}$, Co${\mathrm{Cl}}_{2}$, Fe${\mathrm{Cl}}_{2}$, and Mn${\mathrm{Cl}}_{2}$. Only slight dependence of the spectra on excitation energy is found for three excitation energies employed here. Although the observed gross features of the spectra are consistent with the x-ray photoelectron spectra of these materials, the profiles of the spectra are partly different from those of the x-ray photoelectron spectra. The contribution of the $3p$ electrons of ${\mathrm{Cl}}^{\ensuremath{-}}$ ions to the photoelectron spectra relative to those of the $3d$ electrons of transition-metal ions may be different between extreme ultraviolet and x-ray excitations. Detailed comparison with the x-ray photoelectron spectra has been made to separate the components arising from the $3d$ electrons of transition-metals ions. Their line shapes are in good agreement with the spectral distributions of the multiplet levels of the $3d$ electrons in the final states derived from a simple ligand-field treatment.

The energy distribution of the 4 f partial density of states in CeCu 6 has been observed by means of the resonant enhancement of the 4 f cross section associated with the excitation of the 4 d electron. The main 4 f line is located 2.3 eV below the Fermi edge. In addition to the main line, states with the 4 f character are distributed all over the valence band. The 3 p -3 d resonances of the Cu 3 d band and its satellite are also found.

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.

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.

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.

We have constructed a cylindrical drift chamber with anode and cathode delay-line readouts, which is the innermost tracking device of the TOPAZ detector. This inner drift chamber (IDC) is used for the tracking of charged particles in both rφ and rz planes. Fast track-finding logics have been developed for the event triggering. We describe the design, the construction and the performances of the IDC in the first beam run.

The weak 3 p -3 d resonance in the photoemission of MnP observed around the threshold of the Mn 3 p excitation shows an “energy-band-type” aspect, i.e. the coherent decay of the photoproduced electron-3 p -hole pair into the ionization of a single valence band electron. The resonance occurs all over the valence-band region but no satellite due to the two-hole bound state is found. An appreciable fraction of the apparent resonant enhancement in the bands arising from the 3 s and 3 p states of P is ascribed to the superimposed M 2,3 M 4,5 M 4,5 super-Coster-Kronig band. The valence-band spectra show no significant change in the spectral shape as measured above and below the Curie temperature.

In order to provide a standardized control for the data acquisition system of the TOPAZ detector, a Timing Server/Receiver scheme was developed. The entire system is under control of the Interrupt Control Section, which manages an integral operation of the data acquisition system in the FASTBUS environment.

The energy states of 4 f electrons in Ce x La 1- x Cu 6 ( x =0, 0.2, 0.5, 0.8, 1) have been studied by means of resonant photoemission. At any concentration of cerium ions, the energy distribution of 4 f partial density of states shows a leading peak with a skew Lorentzian shape and weak features on both sides of the peak. As the concentration of cerium ions increases, the width of the leading peak increases and its position moves toward the low binding energy, and the 4 f partial density of states per cerium atom near the Fermi edge increases. Fine structures near the 4 d threshold in photoyield spectra have also been observed. The shape of the 3 D 1 line of the lanthanum ion varies with the concentration of lanthanum ions. The origin of the observed dependence of energy distribution curves and photoyield spectra on the concentration of cerium ions is discussed.

The extreme ultraviolet absorption spectra of K, Rb, and Cs show spikes at the thresholds of outermost- p -shell absorption. With inclusion of the data on Nareported by Haensel et al. , it is concluded that the occurrence of a spike at the edge of the absorption spectrum of outermost- p -shell electrons is a commoncharacteristic of alkali metals. In Rb and Cs no definite spike is found at the onset of the high-energy-component-absorption, L II , produced by the spin-orbit splitting of the levels of core holes. The sharpness of the spike decreases in the order of Na, K, Rb, and Cs. The threshold exponent α 0 for the transition to the s -symmetric state, obtained by neglecting the contribution from the transition to the d -symmetric state, decreases as the electron gas parameter, r s , increases in contrast with the prediction from the electron gas theory.

Using synchrotron radiation, photoelectron energy distribution curves in the valence band region have been measured on sintered polycrystalline YBa2Cu3O6.9 and YBa2Cu3O6.0 at liquid nitrogen temperature. Spectra measured on scraped clean surfaces are found to be reproducible. Overall spectra shapes coincide with the energy-band density-of-states curves calculated by the full potential linear augmented plane wave method, provided the locations of the bands are shifted by 1.0 eV. The Fermi edge is recognized in YBa2Cu3O6.9 but not in YBa2Cu3O6.0. The step at the Fermi edge is about one fiftieth as high as the highest peak at 2.3 eV.

Temperature dependence and spectral distribution of photoconductivity in the ultraviolet region of KCl, KBr and NaCl crystals containing U centers have been investigated in the temperature range between room and liquid nitrogen temperatures. The optical absorption spectra of these crystals have also been measured. Two absorption bands are resolved in the shorter wavelength tail of the U band and they are attributed to the transitions to higher excited states of the U center. The spectral distribution of photoconductivity shows maxima at these band peaks. The nature of photocurrent is primary at the temperature range of 190°K–110°K for KCl, 170°K–100°K for KBr and 170°K–90°K for NaCl crystals, respectively, and above and below these temperature ranges the secondary photocurrent appears. The energy gaps between the conduction band and higher excited states of the U center are determined.

The properties of V bands produced by X-irradiation at temperatures above 78°K have been investigated in KBr and KCl crystals. Preferential bleaching with polarized light revealed that many V bands have complicated composite structures in spite of the simplicity of their shapes. The observed dependence of shapes and positions of V bands on the duration of irradiation and the crystal temperature during irradiation are attributed to their composite nature. Some of component bands were found to be destroyed by prolonged X-irradiation. The band which had been called V 4 in KCl was found not to be one corresponding to the V 4 band in KBr.

X-ray photoelectron spectra have been measured on in situ evaporated films of yttrium, lanthanum, and cerium by the use of an electron energy analyser of the parallel plate electrode type. The binding energies of electronic core levels have been determined. Results are compared with the values cited in typical X-ray atomic energy tables. The binding energies of the M 4 (3 d 3/2 ) and M 5 (3 d 5/2 ) levels of lanthanum and cerium as well as the N 2 (4 p 1/2 ) and N 3 (4 p 3/2 ) levels of lanthanum are all found to be split into two components. Possible origins of the splitting are discussed, although no definite conclusion is drawn out.

The optical absorption spectra of MnCl 2 , FeCl 2 , CoCl 2 , and NiCl 2 have been measured over the energy range from 2 to 30 eV. The gross features of the spectra, especially broad bands above 10eV, are alike in all of the four materials. The charge transfer bands due to the electronic transitions from the 3 p level of chlorine to the 3 d and 4 s levels of metal ions and the band due to the 3 d → 4 s transition are assigned in the spectra.

The spectral distribution of photoconductivity has been investigated at liquid nitrogen and liquid helium temperatures both on additively colored and X-rayed CsBr. A peak is always found on the long wavelength side of the F band in the spectral distribution curve of ηω. Absorption bands which are located at 400 and 490 mµ at liquid nitrogen temperature are found to occur only when F centers are present. Absorption of photons in these bands gives rise to photocurrents. The two bands are interpreted as those like the L bands in NaCl-type alkali halides. At liquid helium temperature, fine structure is resolved in the region below 600 mµ. A band, which is photoconductive, is developed on the long wavelength side of the F band by optical bleaching of the F band at liquid nitrongen temperature.

The change in the photoconductivity of KCl crystals containing F centers upon optical bleaching of the F band has been investigated at low temperature. It was shown that the presence of M centers is not responsible for the residue of the photoconductivity in the F band region at low temperature. F ' centers were produced through a tunneling process when F centers were optically excited at low temperature. The quantum yield of the process was dependent on the concentration of F centers and was estimated to be less than 0.06 in a specimen containing 6×10 16 cm -3 of F centers. The residual photoconductivity in the F band region at low temperature was found to result not from the absorption of photons in the F band but from the absorption in a band overlapping the F band. The suggested shape and position of the band are given.

The temperature dependence of the dichroic properties of the M center in KCl crystal was investigated. At the temperatures above 60°C, the thermal reorientation of the M center in the ground state occurs. The measured value of the activation energy for it was 1.0 eV. It was suggested that vacancy clusters may trap free electrons to form new M centers in the course of the bleaching of the M band and this process may be responsible for the temperature dependence of dichroism of the M band.

The profiles of Na + L 23 absorption spectra of sodium halides have been measured in the vicinity of the threshold at room temperature and liquid nitrogen temperature. Apparent depression of the main bands caused by scattered light and second order light was diminished by minimizing the effect of scattered light and correcting the effect of second order light. Sharp doublets at the threshold, which are ascribed to creation of core excitons with holes in the 2 p level of sodium, have large oscillator strengths as compared with other absorption bands in the spectra. The doublet can be decomposed approximately into two Gaussians at room temperature and two Lorentzians at liquid nitrogen temperature. These properties along with the nature of exchange energy between the electron and the hole of the core exciton are interpreted in terms of the electron-lattice and the electron-electron interactions and of the localized nature of the optical excitation involved.

The Cl - L 23 absorption spectra of thin films of CuCl, ZnCl 2 , CdCl 2 , PbCl 2 , MnCl 2 , FeCl 2 , CoCl 2 , NiCl 2 , MgCl 2 , CaCl 2 , SrCl 2 , and BaCl 2 have been measured by the photographic method using synchrotron radiation from a 1.3 Bev electron synchrotron as a soft X-ray source. In all materials studied, other than CaCl 2 , SrCl 2 , and BaCl 2 , the absorption spectra near the threshold show absorption bands probably due to the creation of excitons with holes in the 2 p level of chlorine. The intense and broad absorption continuum beginning around 211 eV is observed in all materials studied. This absorption is assigned to the atomic excitation of Cl - ions. Discussion is given about the profile of each spectrum.

The x-ray photoelectron spectra of the valence bands of CuCl, CuBr, and CuI have been measured. The spectra show that the valence bands of these materials consist of two branches. The existence of a forbidden band between the two branches and a few additional structures are revealed by the deconvolution of the spectra with a measured instrumental response function. The average $p \ensuremath{-}d$ mixing rates in the valence bands are evaluated by taking the transition matrix elements into account. It is shown that the upper branch of the valence bands arises mostly from the $3d$ states of a cuprous ion, in accordance with the optical-absorption spectra in the ultraviolet region. The results are compared with other experimental and theoretical data. Especially, the fundamental absorption spectra are reinterpreted.

Large-angle cross sections for ..gamma..d..--> pi../sup 0/d are systematically measured in a photon energy range between 500 and 1000 MeV. A good fit is obtained by use of a Glauber model calculation which includes the dibaryon resonances /sup 3/F/sub 3/(2.26) and /sup 1/G/sub 4/(2.51), but the fit has an unusual nature in the role of resonance and nonresonance contributions.

The comparison between the optical absorption spectra due to the 4d → 4f transition and the photoemission lines due to 4d electrons in lanthanum and cerium shows that a simple band theoretical interpretation cannot be applied to the 4d → 4f transition.

A toroidal mirror has been produced and used as a prereflector in the optical system of the soft X-ray spectroscopy. The mirror reduces the astigmatism inherent in a grazing-incidence monochromator and the intensity of radiation available for experiments is appreciably increased. Undesirable higher order radiation which appears in the first order spectrum is found to be efficiently removed when the mirror is used in the high energy spectral region. Critical cut-off wavelength in a few materials is discussed.