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Intensity Parameters (intensity + parameter)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Resonant scattering of a photon by an electron in the field of a circularly polarized electromagnetic wave

LASER PHYSICS LETTERS, Issue 4 2005
A. I. Voroshilo
Abstract This paper presents, for general relativistic case, a theoretical study of Compton effect in the field of a circularly polarized wave under resonant condition , resonances related to a virtual intermediate particle that falls within the mass shell. We derive the expressions for the resonant amplitude and the differential cross section when the invariant intensity parameter of the wave is small (, , 1) and absent interference of the scattering and annihilation reaction amplitudes. It is demonstrated that the resonant cross section of scattering may be several orders of magnitude higher than the cross section of Compton effect in the absence of the external field. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Spectroscopic properties of La3Ga5SiO14:Er3+ (1%) crystals

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 11 2006
Zeng M. Wang
Abstract Single crystals of Erbium (Er) doped La3Ga5SiO14 (LGS) have been grown along c-axis by using the Czochralski method. The absorption and fluorescence spectra of LGS: Er3+ single crystals have been measured and analyzed according to the Judd-Ofelt theory. When applied, the following spectral parameters have been obtained: intensity parameters ,t, ,2= 2.741674×10 -20cm2, ,4= 0.66934×10 -20 cm2 and ,6= 0.592591×10 -20 cm2, radiative transition probabilities AJ,J", PJ,J". The radiative lifetime of levels 4I13/2, 4H9/2, 4S3/2 are 11.333ms, 0.447ms and 0.704ms, respectively. The fluorescence branching ratios and the integrated emission cross sections are also calculated. The results suggest that LGS: Er crystals have potential applications as a laser material. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [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]

A Model-Based Approach for Making Ecological Inference from Distance Sampling Data

BIOMETRICS, Issue 1 2010
Devin S. Johnson
Summary We consider a fully model-based approach for the analysis of distance sampling data. Distance sampling has been widely used to estimate abundance (or density) of animals or plants in a spatially explicit study area. There is, however, no readily available method of making statistical inference on the relationships between abundance and environmental covariates. Spatial Poisson process likelihoods can be used to simultaneously estimate detection and intensity parameters by modeling distance sampling data as a thinned spatial point process. A model-based spatial approach to distance sampling data has three main benefits: it allows complex and opportunistic transect designs to be employed, it allows estimation of abundance in small subregions, and it provides a framework to assess the effects of habitat or experimental manipulation on density. We demonstrate the model-based methodology with a small simulation study and analysis of the Dubbo weed data set. In addition, a simple ad hoc method for handling overdispersion is also proposed. The simulation study showed that the model-based approach compared favorably to conventional distance sampling methods for abundance estimation. In addition, the overdispersion correction performed adequately when the number of transects was high. Analysis of the Dubbo data set indicated a transect effect on abundance via Akaike's information criterion model selection. Further goodness-of-fit analysis, however, indicated some potential confounding of intensity with the detection function. [source]