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5 results on '"CONTINUOUS ABSORPTION"'

1. Semiclassical Description of Radiative Processes Involving Heteronuclear Molecular and Quasimolecular Rare Gas Ions.

Author

Kislov, K. S., Narits, A. A., and Lebedev, V. S.

Subjects
*NOBLE gases, *MASS attenuation coefficients, *IONS, *RADIATION absorption, *DIATOMIC molecules, *SEMICLASSICAL limits
Abstract

We report the results of theoretical studies of radiative processes involving heteronuclear rare gas ions formed in low-temperature plasmas of noble gas mixtures. The continuous absorption of light by such molecular and quasimolecular ions occurs as a result of a number of nonadiabatic bound–bound, bound–free, free–free, and free–bound transitions between their ground and excited electronic terms. The main emphasis in the work is put on the development of a self-consistent semiclassical theory of such processes, taking into account the contributions of all rovibrational levels and continuum states of such ions. Our approach is based on the theory of nonadiabatic transitions between potential energy curves of diatomic molecules combined with the approximation of a quasicontinuum for their rovibrational levels. Nonadiabatic free–free and free–bound transitions in asymmetric collisions of heavy rare gas atomic ions with atoms of a buffer rare gas are described in a similar way. We use analytical formulas derived in this work to carry out calculations of the continuous absorption processes involving ArXe+ and KrXe+ ions with sufficiently low and moderate dissociation energies ( D 0 ArXe + = 184 meV and D 0 KrXe + = 396 meV). The competition of different reaction channels in the total absorption coefficient is discussed. The results obtained demonstrate importance of studied radiative processes in the formation of continuous absorption of electromagnetic radiation in plasmas of noble gas mixtures. [ABSTRACT FROM AUTHOR]

Published
2022
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2. Valence band circular dichroism in non-magnetic Ag/Ru(0001) at normal emission

Author

Mascaraque Susunaga, Arantzazu, Mentes, T. Onur, McCarty, Kevin F, Marcos, José, Schmid, Andreas K., Locatelli, Andrea, Figuera, Juan de la, Mascaraque Susunaga, Arantzazu, Mentes, T. Onur, McCarty, Kevin F, Marcos, José, Schmid, Andreas K., Locatelli, Andrea, and Figuera, Juan de la

Abstract

© Institute of Physics This research was supported by the U.S. Department of Energy under contracts No. DEAC04-94AL85000 and DE-AC02-05CH11231 and by the Spanish Ministry of Science and Innovation under Projects No. MAT2009-14578-C03-01 and No. FIS2007-64982., For the non-magnetic system of Ag films on Ru(0001), we have measured the circular dichroism of photoelectrons emitted along the surface normal, the geometry typically used in photoemission electron microscopy. Photoemission spectra were acquired from micrometer-sized regions having uniformly thick Ag films on a single, atomically flat Ru terrace. For a single Ag layer, we find a circular dichroism that exceeds 6% at the d-derived band region around 4.5 eV binding energy. The dichroism decreases as the Ag film thickness increases to three atomic layers. We discuss the origin of the circular dichroism in terms of the symmetry lowering that can occur even in normal emission., US Department of Energy, Spanish Ministry of Science and Innovation, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Published
2023

3. Measuring optical activity in the far-field from a racemic nanomaterial: Diffraction spectroscopy from plasmonic nanogratings

Author

Ventsislav K. Valev, Christian Kuppe, Alexander W. A. Murphy, Joel T. Collins, Sergey N. Gordeev, Xuezhi Zheng, Guy A. E. Vandenbosch, Calum Williams, Williams, Calum [0000-0002-6432-6515], and Apollo - University of Cambridge Repository

Subjects
Diffraction, Technology, Circular dichroism, Materials science, Materials Science, Materials Science, Multidisciplinary, Nanotechnology, CIRCULAR-DICHROISM, ANGULAR-DISTRIBUTION, CONTINUOUS ABSORPTION, CHIRAL MOLECULES, Nanomaterials, General Materials Science, Nanoscience & Nanotechnology, PHOTOEMISSION, Spectroscopy, PHOTOELECTRONS, Plasmon, 40 Engineering, chemistry.chemical_classification, Quantitative Biology::Biomolecules, Science & Technology, Chemistry, Physical, Biomolecule, AMPLIFICATION, Characterization (materials science), Chemistry, chemistry, Physical Sciences, Science & Technology - Other Topics, Chirality (chemistry), 4006 Communications Engineering
Abstract

Recent progress in nanofabrication has redrawn the boundaries of the applicability of chiroptical (chiral optical) effects. Chirality, often expressed as a twist in biomolecules, is crucial for pharmaceuticals, where it can result in extremely different chemical properties. Because chiroptical effects are typically very weak in molecules, plasmonic nanomaterials are often proposed as a promising platform to significantly enhance these effects. Unfortunately, the ideal plasmonic nanomaterial has conflicting requirements: its chirality should enhance that of the chiral molecules and yet it should have no chiroptical response on its own. Here, we propose a unique reconciliation to satisfy the requirements: a racemic plasmonic nanomaterial, consisting of equal amounts of opposite chiral unit cells. We show how diffraction spectroscopy can be used to unveil the presence of chirality in such racemic nanogratings in the far-field. Our experiments are supported by numerical simulations and yield a circular intensity difference of up to 15%. The physical origin is demonstrated by full wave simulations in combination with a Green's function – group-theory-based analysis. Contributions from Circular Dichroism in the Angular Distribution of Photoelectrons (CDAD) and pseudo/extrinsic chirality are ruled out. Our findings enable the far-field measurement and tuning of racemic nanomaterials, which is crucial for hyper-sensitive chiral molecular characterization.

Published
2019
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4. DEPRESSION IN THE CONTINUOUS SPECTRUM OF SOLAR RADIATION IN THE REGION 6500 − 8200˚A

Author

N. L. Tyshko and O. M. Stelmakh

Subjects
Physics, lcsh:Astronomy, Infrared, Continuous spectrum, Photoionization, Radiation, lcsh:QB1-991, cross-sections, continuous absorption, solar radiation intensity, Excited state, Principal quantum number, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, Absorption (electromagnetic radiation), Radiant intensity
Abstract

Based on the authors’ computations of cross-sections of the basic processes which form continuous absorption in the photospheres of solar-type stars, the spectral dependence of the solar radiation intensity in the continuous spectrum in the visible and infrared regions has been investigated. It is shown that the depression observed in the continuous spectrum of solar radiation in the region (6500 − 8200) ˚A is caused by the processes of photoionization of neutral hydrogen atoms excited up to the energy levels with the principal quantum number n = 3. The results of computation are in good agreement with the data observed.

Published
2015
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5. DEPRESSION IN THE CONTINUOUS SPECTRUM OF SOLAR RADIATION IN THE REGION 6500 − 8200˚A

Author

Stelmakh, O. M., Tyshko, N. L., Stelmakh, O. M., and Tyshko, N. L.

Abstract

Based on the authors’ computations of cross-sections of the basic processes which form continuous absorption in the photospheres of solar-type stars, the spectral dependence of the solar radiation intensity in the continuous spectrum in the visible and infrared regions has been investigated. It is shown that the depression observed in the continuous spectrum of solar radiation in the region (6500 − 8200) ˚A is caused by the processes of photoionization of neutral hydrogen atoms excited up to the energy levels with the principal quantum number n = 3. The results of computation are in good agreement with the data observed.

Published
2016

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