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Spectral Position (spectral + position)

Distribution by Scientific Domains

Physics and Astronomy	80%

Selected Abstracts

THE APPLICATION OF ELECTRON SPIN RESONANCE AS A GUIDE TO THE MATURATION AND TYPING OF ORGANIC MATTER IN THE NORTH SEA

JOURNAL OF PETROLEUM GEOLOGY, Issue 1 2003
R. A. McTavish
In early electron spin resonance (ESR) analysis of North Sea wells, maturation of organic matter (OM) was expressed in terms of maximum palaeotemperature (MPT) based on North American calibrations that did not consider the influences of kerogen composition or overpressure. In the North Sea, the MPTs were anomalous in overpressured sequences and relative to other indices of OM maturation such as vitrinite reflectance, so the ESR method was abandoned there in geochemical studies. However, early empirical study of North Sea ESR data indicated that, in relation to functions that linked temperature and pore pressure, some ESR parameters were predictable without reference to MPTs. In order to re-evaluate ESR parameters as indices of OM maturation, the physical factors (temperature and pressure) which affect OM maturation are related in the present paper to the ESR parameters "g" (spectral position) and Ng (spin density) at six well locations in the northern North Sea. A third ESR parameter, W (line width), is not an effective guide to maturation levels due to its complex relationship to the physical factors and kerogen types. However, cross-plots of W versus "g" and Ng appear to be as effective as pyrolysis for kerogen typing. Levels of maturation investigated in the North Sea wells range through the equivalent vitrinite reflectance values of about 0.50,1.50%. The values of "g" and Ng have been differentiated for kerogen type, but undifferentiated values of "g" have also been studied. Regression analysis has shown that there are linear relationships between the ESR parameters "g" and Ng, and the physical factors present-day temperature (To), "effective" temperature (Te), and differential pressure (Pd). Correlation coefficients for both "g" (undifferentiated and differentiated) and Ng (differentiated) relative to the physical factors are high; the highest values are for "g" and Ng relative to Te and Pd (r =,0.950 for "g" differentiated or undifferentiated, r = 0.944,0.976 for Ng differentiated, respectively). However, correlation coefficients were lower for "g" and Ng relative to To. More frequent high correlation coefficients and larger sample populations suggest that "g" (undifferentiated) is a more reliable index of OM maturation than Ng(differentiated). However, the estimation of levels of OM maturation is improved if both indices are used together. The ESR method appears to be effective both for estimating levels of OM maturation and for kerogen typing. It has a number of potential advantages over other geochemical methods: firstly, it is more sensitive for estimating OM maturation than most other methods; secondly, it can be used to analyze organic matter which is as old as Proterozoic; thirdly, it does not destroy the samples analyzed. [source]

Plasmon induced modification of the transverse magneto-optical response in Fe antidot arrays

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 10 2010
J. F. Torrado
Abstract In this Letter we present the effects that the excitation of plasmon-like modes in periodically perforated Fe films have over the Transverse Magneto-Optical Kerr Effect (TMOKE). The excitation of the modes gives rise to clear signatures in the TMOKE spectra. We analyze the spectral position of the structures as a function of both the polar and azimuth angle. Schematic representation of the system, and TMOKE signal for a Fe membrane along , = 0°. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Submicron resolution carrier lifetime analysis in silicon with Fano resonances

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010
Paul Gundel
Abstract Defect rich regions in multicrystalline silicon are investigated by Raman spectroscopy at high and low injection levels. By analyzing the Fano type asymmetry and the spectral position of the first order Raman peak crucial properties such as recombination lifetime, doping density and stress can be extracted simultaneously. Due to the small wavelength of the excitation laser the spatial resolution of these measurements is significantly below 1 µm, which gives new insight into the impact of defects on the carrier recombination lifetime. The results are evaluated by comparing them to micro-photoluminescence and synchrotron X-ray fluorescence measurements. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Microcavity modified spontaneous emission of single quantum dots

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2007
G. S. Solomon
Abstract We summarize our earlier research showing how the radiative properties of an individual InAs quantum dot exciton state can be altered by their spatial and spectral position with respect to a discrete semiconductor microcavity mode. The InAs quantum dot is formed epitaxially in GaAs, and the microcavity is processed from a one-wavelength distributed Bragg reflector planar microcavity of GaAs and AlAs to form a sub-micrometer diameter pillar. Two states are tuned through a discrete cavity mode through sample temperature changes and show a spontaneous emission enhancement of 4. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Quantum beats between magnetic field split states in semiconductor microcavity

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2005
M. N. Makhonin
Abstract Spin properties of quantum well excitons in the active layer of planar micricavity have been analyzed using pump-and-probe technique in magnetic fields normal to the cavity plane. When exciting the cavity polaritons with linearly polarized ps pulses the differential transmission (DT) spectra show a time oscillation both in the DT signal, IDT, and spectral position of ,+ and ,, polarized lower polariton (LP) states E+ and E,. The oscillation in IDT and E+ - E, is inverse in the magnetic field and shown to be controlled by rotating the LP polarization plane due to the difference in the ,+ and ,, LP energies. The period coincides for IDT and E+ - E, whereas the phase of their oscillation differs from each other by ,/4. The decay of quantum beats increases with excitation density due to an enhanced interparticle scattering. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]