Five-level Atom Research Articles

Dynamics of Five-Level Atoms in Two Standing Electromagnetic Waves

We examine the dynamics of five-level atoms interacting with two standing waves. In our approach we describe the motion of the atoms by a Fokker-Planck equation, including the effect of velocity-dependent two-photon Raman processes within the second order rate equation approximation. By using this procedure we numerically calculate the cooled temperatures of sodium atoms. We then find two principal types of behaviour; that of two-level and three-level atomic systems. We are also able to find detunings of the standing waves for which the atoms are cooled to temperatures below the “Doppler limit”.

A generalized Jaynes-Cummings model for the N-level atom and (N − 1) modes

Abstract A generalized Jaynes-Cummings model is presented to discuss the interaction between an N -level atom and ( N − 1) modes of the radiation field. The level to which the rest of the levels are connected lies in the middle. A detuning parameter is introduced to make the model solvable. Distribution and characteristic functions and different statistical averages are calculated. Multiphoton processes are discussed. The system of a three-level atom and two modes with its three different configurations, and a configuration of the system of a five-level atom and four modes are considered under specified initial atomic conditions. The interaction with squeezed modes of light is investigated. The dependence of the features of the phenomenon of collapses and revivals on the configuration of the system, the atomic initial conditions, the detuning parameter and the statistical aspects of the interacting squeezed modes are shown.

Hydrogen emission from moving solar prominences

Brightness variations of the lines arising from a five-level hydrogen model atom, depending upon prominence velocities, have been investigated using a combination of two non-LTE techniques. The importance of the Doppler brightening and/or Doppler dimming effects is demonstrated for the lines of the Lyman and Balmer series.

Theoretical quasar emission-line ratios. VII - Energy-balance models for finite hydrogen slabs

view Abstract Citations (31) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Theoretical quasar emission-line ratios. VII. Energy-balance models for finite hydrogen slabs. Hubbard, E. N. ; Puetter, R. C. Abstract The authors present energy-balance calculations for finite, isobaric, hydrogen-slab quasar emission-line clouds which incorporate probabilistic radiative transfer (RT) in all lines and bound-free continua of a five-level plus continuum model hydrogen atom. They discuss the resulting line ratios, regions of line formation, level populations, and range of applicability of the models. The calculations neglect the effects of heavy elements and secondary ionizations from primary photoelectrons. An appendix presents a detailed comparison of differences between four different methods of treating the radiative transfer: (1) the probabilistic method, (2) an exact RT solution, (3) an effective two-level ρ = pe energy-balance calulation, and (4) a ρ = pe calculation explicitly incorporating indirect photon creation and destruction paths. Publication: The Astrophysical Journal Pub Date: March 1985 DOI: 10.1086/162997 Bibcode: 1985ApJ...290..394H Keywords: Balmer Series; Emission Spectra; Hydrogen Clouds; Quasars; Radiative Transfer; H Alpha Line; Lyman Spectra; Photoionization; Seyfert Galaxies; Thermodynamic Equilibrium; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1) Related Materials (8) Part 1: 1981ApJ...243..381C Part 2: 1981ApJ...243..390C Part 3: 1981ApJ...248...82C Part 4: 1982ApJ...256..798C Part 5: 1981ApJ...251..446P Part 6: 1982ApJ...260...44P Part 7: 1982ApJ...258...46P Part 9: 1985ApJ...295..394P

Flare model chromospheres and photospheres

Homogeneous plane-parallel model atmospheres for solar flares have been constructed to approximately simulate observations of flares. The wings of the Ca II lines have been used to derive flare upper photosphere models, which indicate temperature increases of ∼100 K over the temperature distribution in the pre-existing facula at a height of 300 km above τ5000 = 1. In the case of flares covering sunspots the temperature rise seems to occur much higher in the atmosphere. We solve the transfer and statistical equilibrium equations for a three-level hydrogen atom and a five-level calcium atom in order to obtain the chromospheric flare models. The general properties of flares, including ne, N2, linear thickness, and Lyman continuum intensity are approximately reproduced. We find that with increasing flare importance the height of the upper chromosphere and transition region occur lower in the solar atmosphere, accounting for the factor of 60–600 increase in pressure in these regions relative to the quiet Sun. The Ca II line profiles agree with observations only by assuming a macro-velocity distribution that increases with height. Also the chromospheric parts of flares appear to be highly inhomogeneous. We show that shock and particle heated flare models do not agree with the observations and propose a thermal response model for flares. In particular, it appears that heating in the photosphere is an essential aspect of flares.

Computer Program for a Steady-State Gas.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Computer Program for a Steady-State Gas. Johnson, Hollis R. Abstract In radiating gases of interest in astrophysics the existence of strict (or even "local") thermodynamic equilibrium is questionable. The absence of such equilibrium leads to departures from the equilibrium distribution functions, but quantitative estimates of the amount of these departures have not been established for many interesting cases. In general, the answer requires the solution of the set of equations expressing steady state in the atomic energy levels and the set of equations of radiative transfer through the gas. A computer program which will permit comprehensive calculations of steady-state equilibrium in a self-consistent fashion is described. The complete program performs these operations: (1) Determines the monochromatic optical depth Ty (To), where r0 is some standard optical depth, using as input the absorption coefficients Ky and K0 throughout the atmosphere. (2) Finds J(v,T0), the mean intensity, at all wavelengths of interest and at many points throughout the atmosphere from the integral equation. Input for this program are S(v,m) and rp(To), where S is the source function. (3) Calculates the integral of the mean intensity and the absorption coefficient over frequency for all transitions of interest at many values of r0. Input are J(v,T0) and the absorption coefficients as functions of frequency. (4) Solves the steady-state equations to obtain at a number of points in T0 the population of the energy levels, ~~, and S~. The input data are the radiation fields (step 3), atomic parameters, collisional and radiative cross sections, and the temperature and density throughout the gas. An application of the program is made to obtain a self-consistent solution for neutral helium in the shell surrounding a star. A five-level model atom is employed in an atmosphere of constant T0= 100000, N(He) =1011 cm-3, and N0=1012 cm-3 which is excited by a B star. Publication: The Astronomical Journal Pub Date: November 1962 DOI: 10.1086/108776 Bibcode: 1962AJ.....67..578J full text sources ADS |