Satoru Sugano

Absorption Spectra of Cr3+ in Al2O3 Part A. Theoretical Studies of the Absorption Bands and Lines

In the frame-work of the crystalline field theory, the excited states of Cr 3+ in Al 2 O 3 and the optical transitions to these states are studied taking into account the effect of trigonal field and spin-orbit interaction. Initial splittings and optical anisotropies of the broad band (transitions to quartet states) and the sharp lines (transitions to doublet states) are examined. For the sharp lines, the Zeeman effect is also examined and the Zeeman patterns are predicted. Comparing these theoretical results with those of the experimental ones given in Part B, the assignments of U , Y bands and R 1 , R 2 , B 1 , B 2 lines have been established. It is shown that the g -shifts of the excited doublets observed in the Zeeman patterns can also be explained under such assignments. It is also shown that the experimental data of the optical absorption can be reasonably connected to those of the paramagnetic resonance absorption.

Interband Optical Transitions in Extremely Anisotropic Semiconductors : I. Bound and Unbound Exciton Absorption

By using the effective-mass theory for exciton, the allowed and forbidden direct interband transitions in extremely anisotropic semiconductors are discussed. In this case, the problem is reduced to solving the Schrodinger equation for a hypothetical two-dimensional hydrogen atom. The bound and unbound solutions of the equation are obtained, and the absorption intensities in the discrete, quasi-continuous, and continuous spectral regions are calculated. It is shown that, in the allowed transitions, a small peak may appear just above the absorption edge because of the Coulomb interaction between an excited electron and a hole. This result is compared with the experimental curves of the absorption in layer-type semiconductors, CaS, GaSe, and GaTe.

Discrete Variational X α Cluster Calculations. III. Application to Transition Metal Complexes

The discrete variational cluster calculations for perovskite type compounds KMeF 3 (Me=Cr, Mn, Fe, Co, Ni and Cu) and manganese dihalides MnX 2 (X=F, Cl and Br) have been made using the spin-polarized X α scheme. The calculated values of 10 D q and the transferred hyperfine constants are in good agreement with experiment. The d level splitting by the spin polarization is in accordance with the estimation from experimental Racah parameters. The level structure of the cluster is greatly improved by taking into account the potential from ions outside of the cluster, and shows good agreement with valence state XPS spectrum. The calculated excitation energies from ligand p to empty d and to conduction band can explain very well the u.v. spectra for MnX 2 . The halogen 3 d and 4 d are found to be important in level structures both for valence and lower excited regions of MnCl 2 and MnBr 2 .

Absorption Spectra of Cr3+ in Al2O3 Part B. Experimental Studies of the Zeeman Effect and Other Properties of the Line Spectra

The absorption intensities, widths and wave-numbers of R 1 , R 2 and B 1 B 2 lines of Cr 3+ in ruby for the polarized light E ⊥ C 3 and E // C 3 are experimentally studied at 20°K and 4.2°K. Zeeman effect is also studied, using a magnetic field H 0 =24,000 φ, for both R and B lines. The Zeeman effect has not been observed yet for the B lines, while Lehmann has already observed the Zeeman effect for R lines. In our results of R lines, the quantitative aspects of Lehmanns experiment are improved. The comparison is made with the theoretical results given in Part A and it is shown that nice agreements can be obtained when suitable assignments of the spectra are adopted and when fairly large g -shifts of the excited states are introduced.

Molecular Orbital Analysis of Iron‐Group Cyanides

In the iron‐group cyanides the low‐lying antibonding orbitals of the cyanide ligands do not contain electrons. These π* orbitals play an important role in the covalency of the complexes. A molecular orbital analysis of their role is presented in order to correlate the orbital reduction factors derived from the ESR experiments of Baker, Bleaney, and Bowers with the isomer shifts of the Mossbauer experiments. By fitting the wavefunctions to the ESR experiment it is shown that the Fe2+ complex donates about one more electron to the π* orbitals than does the Fe3+. This shows that the effective charges of Fe2+ and Fe3+ are approximately the same and explains their similar isomer shifts.

Satellites in X-Ray photoelectron Spectra of Transition-Metal Compounds

Appearance of satellite lines in the X-ray photoelectron emission from the 2 p -shell of the metal ion transition-metal compounds are ascribed to the increase of covalency due to the creation of an inner-core hole. For this argument a simple two-configuration model is used, which reveals a shortcoming once ab initio calculations of the line positions and intensities are attempted. The molecular-orbital calculation of multiplet structure of the satellite is performed by taking into account a change of the atomic d -orbital due to the hole in the molecular cluster of (NiF 6 ) 4- , and a reasonable agreement with experiments is obtained. The reduction of the Coulomb-interaction parameters found in the analysis of the main line can also be explained by our theory. The result shows that the conventional equivalent-core approximation overestimates effects of the hole.

Luminescence Processes in the KCl:Tl Phosphor in a Multidimensional Configuration Space

In order to explain the 3050A and 4750A emissions of KCl:Tl phosphor which are raised by excitation in any of the absorption bands, a multi-dimensional configuration coordinate model is introduced. This is achieved by taking into account the Jahn-Teller effect for the excited states of the thallium ion. The Jahn-Teller effect is treated by means of an intermediate coupling scheme within the 6s6p configuration, because the mixing of the 3 P and 1 P states by the spin-orbit interaction is essential to understand the optical properties. It is shown that introduction of a tetragonal distortion of the emission center is able to explain the luminescence processes of this phosphor both semi-quantitatively and qualitatively: Under the tetragonal and trigonal distortions, both the crossing of the pure spin singlet 1 P and triplet 3 P curves and the appearance of two minima in the 3 P 1 energy curves are expected. The former accounts for the non-radiative transition from the 1 P 1 state to the 3 P 1 state and the l...

Covalency in Ionic Crystals: KNiF3

Within the framework of the self-consistent field molecular orbital theory, studies are made of the covalency and the cubic field splitting parameter in ionic crystals, with a particular reference to KNiF 3 . It is pointed out that the effect of the rearrangement among the virtually transfered electron and d -electrons is essential in obtaining proper values of the covalency. By using the Heitler-London theory with an admixed excited configuration, in which atomic orbitals of the metal and ligand ions are different from those in the ground configuration, this effect of the rearrangement can be taken into account to some extent, and a reasonable value of the covalency may be obtained. Finally, by making a one to one correspondence between the expressions in the generalized Heitler-London theory and a simple molecular orbial theory, it is shown that the simple molecular orbital theory could successfully be used if an appropriate effective Hamiltonian is assumed.

Structural fluctuation and atom-permutation in transition-metal clusters

The atomic structure and thermodynamic properties of transition-metal clusters containingN atoms are investigated forN=6 and 7 using the method of molecular dynamics, where Guptas potential taking into account many-body interaction is employed. The caloric curve (total energy — temperature curve) and the structural fluctuations are studied. The “fluctuating state” is found forN=6 in the region of the temperature near below the melting point, where clusters undergo structural transition from one isomer to others without making any topological change. The fluctuating state differs from the coexistence state in that the former involves no atomic diffusion, and goes to a structural phase transition of the bulk whenN is increased. On the other hand, the motion of atom-permutation is found in the low-temperature region of the liquid state, being induced by the cooperative motion of two atoms. It is discussed that such a motion easily occurs along the surface and may be considered to be one of the characteristics of small clusters. The fluctuating state is discussed in relation to the structural fluctuation of gold clusters observed experimentally.

A theoretical approach to rotationally inelastic scattering of a heteropolar rigid rotor by rigid and flat surfaces

Abstract Rotationally inelastic scattering of a rigid rotor, which represents a heteronuclear diatomic molecule, by rigid and flat solid surfaces is investigated by assuming three types of potential. It is demonstrated that the observed Boltzmann-like profile for low excitations in the NO-Ag(111) scattering experiment may be ascribed to the first of the two rotational rainbow peaks. It is also shown that “quasi-trapping” of molecules occurs if the potential has an attractive part.