Analytic expressions for fluorescence spectra and optical collision rates of collisionally perturbed atoms in a strong driving field

1984 ◽  
Vol 62 (2) ◽  
pp. 183-191 ◽  
Author(s):  
F. Schuller ◽  
G. Nienhuis
Keyword(s):  
Collision Operator ◽  
Line Broadening ◽  
Pressure Broadening ◽  
Driving Field ◽  
Field Independent ◽  
Intensity Field ◽  
Analytic Expressions ◽  
Limiting Case ◽  
Optical Collisions ◽  
Weak Fields

We have studied the problem of a collisionally perturbed two-level atom in an intense driving field by developing a method which allows us to calculate the field-dependent collision operator in terms of the low intensity field-independent line-broadening function arising in the usual unified theory of pressure broadening. Our relations are exact to all orders in the field in the limiting case of weak collisions, but they are exact also in the complementary case of strong collisions and weak fields. We apply our results to derive explicit expressions for the rate of optical collisions, the fluorescence spectrum in the case of well-separated components, and the absorption during an adiabatic square pulse.

scholarly journals Electromagnetic responses of relativistic electrons

2018 ◽  
Vol 84 (1) ◽  
Author(s):  
C. A. A. de Carvalho ◽  
D. M. Reis
Keyword(s):  
Dispersion Relation ◽  
Quantum Electrodynamics ◽  
Relativistic Electrons ◽  
Zero Temperature ◽  
Low Frequencies ◽  
One Dimensional ◽  
Electromagnetic Responses ◽  
Analytic Expressions ◽  
Weak Fields ◽  
Recent Claim

We compute the real and imaginary parts of the electric permittivities and magnetic permeabilities of relativistic electrons from quantum electrodynamics at finite temperatures and densities, for weak fields, neglecting electron–electron interactions. For non-zero temperatures, electromagnetic responses are reduced to one-dimensional integrals computed numerically. For zero temperature, we find analytic expressions for both their real/dispersive and imaginary/absorptive parts. As an application of our results, we obtain the dispersion relation for longitudinal electric plasmons. Present calculations support our recent claim that, at low frequencies and long wavelengths, the system will exhibit simultaneously negative electric and magnetic responses.

Some magnetic properties of metals I. General introduction, and properties of large systems of electrons

1952 ◽  
Vol 211 (1107) ◽  
pp. 500-516 ◽  
Keyword(s):  
Thermodynamic Potential ◽  
Final Section ◽  
Finite Size ◽  
Magnetic Behaviour ◽  
General Introduction ◽  
Field Independent ◽  
Explicit Formulae ◽  
Large Systems ◽  
Limiting Case ◽  
Degeneracy Parameter

A general introduction surveying the problems to be examined in a series of papers is followed by a detailed treatment of the magnetic behaviour of a large system of electrons. The Schrödinger equation is solved on the assumption that the system is unbounded, and the modifications caused by the finite size of the system are then determined for the limiting case in which the system is much larger than the electronic orbits. An expression is then obtained for the density of states, and the free energy of the system found assuming that k T < E 0 , where E 0 is the degeneracy parameter. The magnetic susceptibility, thermodynamic potential and specific heat are discussed for the two cases N constant and E 0 constant. Explicit formulae are given for the temperature-dependence of the field-independent term in the susceptibility. In the final section the corrections due to electron spin are introduced.

scholarly journals Pressure Broadening of UV Lines

1971 ◽  
Vol 2 ◽  
pp. 561-565
Author(s):  
H. van Regemorter
Keyword(s):  
Electron Density ◽  
Neutral Hydrogen ◽  
Uv Spectra ◽  
Line Broadening ◽  
Pressure Broadening ◽  
Static Approximation ◽  
Impact Approximation ◽  
Typical Time ◽  
Static Regime ◽  
The Impact

Most of the lines in the UV spectra are lines of ions which are formed in high temperature regions where the pressure broadening is caused by electrons and protons. This is the case in O and B type stars for which the theoretical calculation of the width of all the strong UV lines is important in determining both the blanketing effect and the abundances of the elements.The cores of these strong lines are formed in non-LTE layers near the surface where the electron density is very low. The wings of some of the lines are more easy to interpret, being formed in deeper layers of the star, where one can assume LTE and where the electron density - or in the Sun, the neutral hydrogen density - is such that the pressure broadening is much more important than the natural width.Two opposite approximations have been applied to the line broadening problem; the impact approximation is generally valid for electrons when the perturbations are so rapid that the collision timeτcis very small compared to the typical time, Δω-1, of importance in computing the profile at the frequencyΔω = ω – ω0measured from the line centre. On the contrary, whenτc≫Δω−1the quasi static approximation may be assumed. Both of these approximations have been considerably improved and efforts have been made recently to develop a unified theory valid from the impact regime to the static regime.

Rotation of a rigid diatomic dipole molecule in a homogeneous electric field - II. Energy levels when the field is zero, very weak or very strong

1994 ◽  
Vol 347 (1682) ◽  
pp. 23-35 ◽  
Keyword(s):  
Electric Field ◽  
Energy Levels ◽  
Comprehensive Treatment ◽  
Static Electric Field ◽  
Energy Quantization ◽  
Dipole Molecule ◽  
Free Case ◽  
Limiting Case ◽  
Weak Fields ◽  
Quantization Problem

The energy quantization problem for a rigid diatomic electric dipole molecule in a homogeneous static electric field is considered. The field-free case is treated in some detail, since it is difficult to find a comprehensive treatment in the literature. For the limiting case of very weak fields the available results of conventional perturbation theory are presented in lucid form. For the limiting case of very strong fields an easily survey able perturbation calculation is performed.

scholarly journals Isolated Objects and Their Evolution: A Derivation of the Propagator’s Path Integral for Spinless Elementary Particles

2022 ◽  
Vol 52 (1) ◽  
Author(s):  
Domenico Napoletani ◽  
Daniele C. Struppa
Keyword(s):  
Time Reversal ◽  
Equivalence Principle ◽  
Relativistic Effects ◽  
Elementary Particles ◽  
State Variables ◽  
Consistent Theory ◽  
General Potential ◽  
Limiting Case ◽  
Weak Fields ◽  
Spacetime Paths

AbstractWe formalize the notion of isolated objects (units), and we build a consistent theory to describe their evolution and interaction. We further introduce a notion of indistinguishability of distinct spacetime paths of a unit, for which the evolution of the state variables of the unit is the same, and a generalization of the equivalence principle based on indistinguishability. Under a time reversal condition on the whole set of indistinguishable paths of a unit, we show that the quantization of motion of spinless elementary particles in a general potential field can be derived in this framework, in the limiting case of weak fields and low velocities. Extrapolating this approach to include weak relativistic effects, we explore possible experimental consequences. We conclude by suggesting a primitive ontology for the theory of isolated objects.

THE TWO-ATOM DICKE MODEL IN A SQUEEZED VACUUM: THE FLUORESCENT SPECTRUM INCLUDING DIPOLE-DIPOLE INTERACTION

1991 ◽  
Vol 05 (19) ◽  
pp. 3115-3125 ◽  
Author(s):  
R.R. PURI ◽  
AMITABH JOSHI ◽  
R.K. BULLOUGH
Keyword(s):  
Master Equation ◽  
Spectral Characteristics ◽  
Dipole Interaction ◽  
Resonance Fluorescence ◽  
Driving Field ◽  
Squeezed Vacuum ◽  
Fluorescent Spectrum ◽  
Analytic Expressions ◽  
Atomic Dipole ◽  
Dicke Model

The spectrum of resonance fluorescence from a system of two identical coherently driven two-level atoms interacting with a broadband squeezed bath is studied by including the atomic dipole-dipole interaction. The spectral characteristics are studied by solving the master equation numerically and also by deriving the analytic expressions in the limit of strong driving field.

scholarly journals Effect of pressure broadening on the radiative heat transfer by CO and CH4 gases using line by line method with latest high-temperature database

2021 ◽  
pp. 319-319
Author(s):  
Yu Yang ◽  
Shu Zheng ◽  
Yuzhen He ◽  
Mingxin Xu ◽  
Zixue Luo ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Absorption Coefficient ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Pressure Effect ◽  
Pressure Effects ◽  
Line Broadening ◽  
Pressure Broadening ◽  
Elevated Pressures

As the development of current propulsion technology such as gas turbine and rocket chamber moving to higher working pressure, the radiative parameters of fuel, such as CH4or CO, are required at elevated pressures, which in some cases are calculated without considering the pressure effect of line broadening. To investigate the pressure effect of line broadening on the radiative heat transfer, the radiative heat sources of a one-dimensional enclosure filled with CH4/CO and Planck mean absorption coefficients at elevated pressures were calculated using the statistical narrow band(SNB)and line by line (LBL)methods. The radiative parameters were conducted using high-temperature molecular spectroscopic(HITEMP)2019 (for CO) and HITEMP 2020 (for CH4) databases. The results showed that the pressure effect of line broadening on the calculations of radiative heat source of CH4can be ignored when HITEMP 2020 database was used. For CO medium, the pressure effect of line broadening was over 40% at 30 atm in all cases whichever methods and databases were used. The pressure broadening has a strong effect on the Planck mean absorption coefficient below 1000 K for CH4 and at the temperature of 500-900K for CO at 30 atm. The maximum pressure effects were 22% for CH4 and 18% for CO at 30 atm, which illustrated the pressure effect of line broadening needed to be taken into account in the calculation of Planck mean absorption coefficient.

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