Communications in Theoretical Physics
By means of improved ligand-field theory, the "pure electronic" presure-induced shifts (PSs) and the PSs due to electron-phonon interaction (EPI) of the R-1, R-2, B-1, B-2, B-3, and R-3' lines and the ground-state zero-lield-splitting' of ruby have been uniformly calculated. The calculation results are in very good agreement with all the experimental data. At normal pressure, ruby is a crystal with very strong crystal field. Thus the admixture of vertical bar t(2)(2)(T-3(1))e(4)T(2)> and vertical bar t(2)(32)E > bases in the wavefunction of R-1 level of ruby is small at normal pressure, and it gradually decreases with increasing pressure, which causes the R-1-line PS of ruby to monotonously red shift with approximate linearity. The combined effect of the pure electronic PS of R, line and the PS of R, line due to EPI gives rise to the total PS of R, line. The analyses and comparisons among the features of R-1-line PSs of three laser crystals (ruby, GSGG:Cr3+ and GGG:Cr3+) have been made, and the origin of their difference has been revealed.
关键词:
high-pressure effect;electron-phonon interaction;R;R ';and B;line-groups;ground-state zero-field-splitting;admixture of;[t(2)(2)(T-3(1))e(4)T(2)) and [t(2)(3)(2) E);laser crystal;calibration;spectra
Chinese Physics Letters
The electron paramagnetic resonance spectra of trigonal Mn(2+) centers in ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) crystals are studied on the basis of the complete energy matrices for a d(5) configuration ion in a trigonal ligand field. It is demonstrated that the local lattice structure around a trigonal Mn(2+) center has an elongation distortion along the crystalline c(3) axis, and when Mn(2+) is doped in the ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) crystals, there is a similar local distortion. From the EPR calculation, the local lattice structure parameters for trigonal Mn(2+) centers in ZnNbOF(5)center dot 6(H(2)O) and CoNbOF(5)center dot 6(H(2)O) are determined.
关键词:
phase-transition;ions;complexes;crystals;spectra;fe-3+;epr
Chemical Physics Letters
The EPR spectra of octahedral Fe3+ center in lutetium aluminum garnet have been studied by means of the complete energy matrices for a d(5) configuration ion in a trigonal ligand-field. It is manifested that the local lattice structure around an octahedrally coordinated F3+ e center has an expansion distortion from that of undistorted host Al3+ ion. The expansion distortion can be ascribed to the fact that the radius of Fe3+ ion is bigger than that of Al3+ ion, and consequently the Fe3+ ion pushes the oxygen ligands outwards. Simultaneously, for the octahedral Fe3+ center in the crystal, the local lattice structure parameters, R = (2.007 +/- 0.022) A and theta = (52.708 +/- 0.032)degrees, which reflect the interactions between impurity and crystal lattice, are determined from our calculation, and EPR parameters a, D, and (a - F) also get a unified explanation. (c) 2005 Elsevier B.V. All rights reserved.
关键词:
paramagnetic-resonance;up-conversion;thulium;ions
WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate
,
Lawrence Livermore National Laboratory
,
Livermore
,
CA 94551)
金属学报(英文版)
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
关键词:
: U.S. Materials Science. U.S. National Laboratories and Facilities
,
null
Communications in Theoretical Physics
By using the wavefunctions obtained from diagonalizing the complete d(3) energy matrix at normal and various pressures, the g factor of the ground state of SrTiO3:Cr3+ and its pressure-induced shift have been microscopically calculated. Only by taking the local strains around Cr3+ in SrTiO3:Cr3+ (which are about twice the bulk ones) and corresponding P-chi dependence, can we obtain a good agreement between the calculated result of pressure-induced shift of ground-state g factor and the experimental one. The physical origins of this pressure-induced shift have been explained. It is found that the change of Dq(-1) with pressure makes main contribution to the pressure-induced shift of ground-state g factor of SrTiO3:Cr3+. By using the wavefunctions obtained from diagonalizing the complete d3 energy matrix at normal pressure, the relevant matrix elements and accordingly strain-induced splittings of t(2)(3) E-2 and t(2)(3) (4)A(2) of SrTiO3:Cr3+ have been calculated. The important results of Y-c, Z(c), P-c and Q(c) have also been evaluated. It is the admixtures of basic wavefunctions resulted from the spin-orbit interaction and/or Coulomb interaction and/or Kramers degeneracy that make the strain-induced splittings of the levels nonzero. It is found that there are nonvanishing matrix elements of operators T2 xi, T2 eta and T2 zeta between wavefunctions with positive M-s and those with negative M-s', which have important effects on the strain-induced splittings of the levels.
关键词:
crystal fields;energy spectrum;g factors;high-pressure effect;strain-induced splitting;theoretical calculations;ruby;crystal
