Search results for "electromagnetic [radiation]"
showing 10 items of 873 documents
Photoelectric effect from a metal surface: a revisited theoretical model
1992
The Sommerfeld model extended to include radiation–electron interaction in the regime of highly intense fields is taken as the basis for studying theoretically the laser multiphoton photoelectric effect from a metal surface. Numerical analysis is carried out without approximations other than those inherent in the model itself; the study of the multiphoton aspect of the problem is based on a scheme that is nonperturbative in an essential way. The numerical analysis facilitates insight into the potential and the limits of the model in the interpretation of recent experiments and into the similarities and differences between the metal multiphoton effect and atomic multiphoton ionization. The r…
Doppler-free two-photon spectrum of SF_6 for metrological purposes
1998
We report on our systematic investigation of strong Doppler-free two-photon absorption in the middle infrared. The absorption frequencies for two counterpropagating waves of identical frequencies are predicted. Five of these transitions were observed with sub-Doppler resolution with a sideband CO(2) laser and were measured with 10-kHz accuracy. Knowledge of these strong two-photon absorptions frequencies will allow the improvement of secondary frequency standards in the infrared.
Effect of quantum efficiency on the performance of multijunction tandem cells
2015
New insight into the potential of practical solar cells can be given through alternative modeling approaches like Monte Carlo simulations. In the present work, the performance of three stacks of cells connected in series was examined at different levels of internal quantum efficiency. Incident photons, generated by employing the ASTM G173-03 and E490-00a data sets, are accounted for individually as they interact with the stack of cells. The values of the different bandgaps were chosen from a paper by K. Tanabe (2009), and the performance was studied based on photon dynamics.
Physical principles of the amplification of electromagnetic radiation due to negative electron masses in a semiconductor superlattice
2015
In a superlattice placed in crossed electric and magnetic fields, under certain conditions, the inversion of electron population can appear at which the average energy of electrons is above the middle of the miniband and the effective mass of the electron is negative. This is the implementation of the negative effective mass amplifier and generator (NEMAG) in the superlattice. It can result in the amplification and generation of terahertz radiation even in the absence of negative differential conductivity.
Unusual Optical Properties of the Dense Nonequilibrium Plasma
2006
A concise overview of new optical properties of dense nonequilibrium plasma formed on the solid state target boundary is given. In this chapter, we describe phenomena such as the third harmonic generation in the skin layer, collisionless electron heating in the high frequency skin-effect regime, absorption, and reflection and transmission of radiation by a plasma with anisotropic electron distribution.
Polarization of the Radiation Emitted in GaAs Semiconductors Driven by Far Infrared Fields
2010
The effects due to the mixing of two far infrared electric fields on the harmonic generation process in low doped GaAs bulks are studied by a three dimensional multivalleys Monte Carlo simulation. The conversion efficiency is calculated by using the appropriate Maxwell equation for the propagation of an electro-magnetic wave along a given direction in the medium. In particular, we focus our attention on the polarization of the generated harmonics, by comparing the polarization obtained from the mixing of an oscillating field with a static electric field with that obtained in the presence of two cyclostationary fields, having an integer ratio between the two frequencies. The findings show th…
Measuring the mean value of vibrational observables in trapped ion systems
2002
The theoretical foundations of a new general approach to the measurement problem of vibrational observables in trapped ion systems is reported. The method rests upon the introduction of a simple vibronic coupling structure appropriately conceived to link the internal ionic state measurement outcomes to the mean value of a motional variable of interest. Some applications are provided and discussed in detail, bringing to light the feasibility and the wide potentiality of the proposal.
A phenomenological quark current for the study of the polarized structure function of the nucleon
1995
In the context of the quark model, a phenomenological expression for the electromagnetic interaction is derived in order to study the polarized structure function of the nucleon. The DHG value without hyperfine corrections and the asymptotic behaviour are reproduced.
Modeling the energy thermalization of X-ray photons in a microcalorimeter with superconducting absorber
2003
We present a modeling of the response of a microcalorimeter to the absorption of X-ray photons, based on the main microscopical processes responsible for the energy thermalization. In particular, we have modeled a microcalorimeter with superconducting tin absorber (350 micron x 350 micron x 7 micron) and neutron transmutation doped (NTD) germanium thermistor (75 micron x 50 micron x 150 micron). Such a detector, operated at 60 mK, is expected to achieve a spectral resolution as good as 1 eV FWHM in the soft X-ray energy range, based on the known sources of thermal and electronic noise. Nevertheless, the best spectral resolution measured in laboratory experimental tests is of about 5 eV FWHM…
Branching fraction measurements of arsenic 4p25s-4p3 transitions
2021
Abstract Transition lines of neutral arsenic atom (As I) have been observed in the spectra of stellar and sub-stellar objects. Accurate and reliable data of oscillator strengths of those transitions allow differentiating between different evolution models of those objects. We have measured branching fractions for As I (4p25s-4p3) transition lines in 180–310 nm spectral range with higher increased accuracy using light source powered by inductively coupled radio frequency plasma (RF-ICP) source – not earlier applied in studies of atomic arsenic. The measurements were performed for 7 excited states of As I and compared with data from the literature. We combined them with the selected lifetime …