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Level Scheme (level + scheme)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Photoluminescence studies of isotopically enriched silicon

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2003
D. Karaiskaj
Abstract In this issue's Editor's Choice, the first high resolution photoluminescence (PL) investigations of isotopically pure silicon are reported. The cover figure shows the PL spectrum of the no-phonon transitions of an exciton bound to the neutral aluminum acceptor in 28Si, compared with the corresponding result from natural Si. It is seen that in the isotopically purified material the lines are shifted (as indicated by the horizontal arrow) and are sharper than in natural Si. Moreover, the splitting of the A0 ground state, as shown in the level scheme of the inset, is clearly absent in the 28Si sample, demonstrating that this splitting results from the random isotopic composition in natural Si. The paper is an invited presentation from the 10th International Conference on Shallow Level Centers in Semiconductors (SLCS-10) held in Warsaw, Poland, 24-27 July 2002. This issue of phys. stat. sol. (b) contains a second paper selected as Editor's Choice, entitled "Tunable spin-injection and magnetoconductance in a novel 2DEG-ferromagnet structure" by Y. Jiang and M. B. A. Jalil [2]. [source]

Optical spectra of Tm3+ -doped YAl3(BO3)4 single crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
E. Cavalli
Abstract Flux grown YAl3(BO3)4 (YAB) crystals doped with Tm3+ have been characterised by optical spectroscopy techniques. The absorption and emission spectra in the UV-VIS-NIR region have been measured at 10 and 298 K. The visible emission decay profiles have been measured at room temperature. The low temperature spectra have been used to obtain the energy level scheme of the optically active ion in YAB. The Judd-Ofelt parametrization scheme has been applied to the analysis of the room temperature absorption spectra in order to evaluate the intensity parameters, the branching ratios and the radiative lifetimes of the emitting states. These have been compared with the experimental values. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Dispersion and stability analyses of the linearized two-dimensional shallow water equations in boundary-fitted co-ordinates

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 7 2003
S. Sankaranarayanan
Abstract In the present investigation, a Fourier analysis is used to study the phase and group speeds of a linearized, two-dimensional shallow water equations, in a non-orthogonal boundary-fitted co-ordinate system. The phase and group speeds for the spatially discretized equations, using the second-order scheme in an Arakawa C grid, are calculated for grids with varying degrees of non-orthogonality and compared with those obtained from the continuous case. The spatially discrete system is seen to be slightly dispersive, with the degree of dispersivity increasing with an decrease in the grid non-orthogonality angle or decrease in grid resolution and this is in agreement with the conclusions reached by Sankaranarayanan and Spaulding (J. Comput. Phys., 2003; 184: 299,320). The stability condition for the non-orthogonal case is satisfied even when the grid non-orthogonality angle, is as low as 30° for the Crank Nicolson and three-time level schemes. A two-dimensional wave deformation analysis, based on complex propagation factor developed by Leendertse (Report RM-5294-PR, The Rand Corp., Santa Monica, CA, 1967), is used to estimate the amplitude and phase errors of the two-time level Crank,Nicolson scheme. There is no dissipation in the amplitude of the solution. However, the phase error is found to increase, as the grid angle decreases for a constant Courant number, and increases as Courant number increases. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Fully relativistic analysis of the absorption spectra of Ca3Sc2Ge3O12:Ni2+

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2006
M. G. Brik
Abstract Systematic analysis of the energy level schemes, ground state absorption (GSA) and covalency effects for the Ni2+ ion in Ca3Sc2Ge3O12 was performed. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron method (DV-ME) [K. Ogasawara et al., Phys. Rev. B 64, 115413 (2001)] was used in the calculations. As a result, complete energy level schemes of Ni2+ and its absorption spectra at both possible crystallographic positions (distorted octahedral Sc3+ and tetrahedral Ge4+ positions) were calculated, assigned and compared with experimental data. Energies of the charge transfer (CT) transitions for both positions are estimated. Numerical contributions of all possible electron configurations into the calculated energy states were determined. By performing analysis of the molecular orbitals (MO) population, it was shown that the covalency of the chemical bonds between the Ni2+ and O2, ions increases in passing from the hexa- to the tetra-coordinated complex. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]