On the self-shift and broadening of doppler-free Rydberg 2S spectral lines in alkali atoms

The shift and broadening of Doppler-free, two-photon transitions to Rydberg states of alkali atoms are analyzed for the case of Rb in the framework of a molecular approach to collisions of ground state and Rydberg atoms. The overall features of the observed spectra are determined by the electrostatic interactions between the two atoms and are calculated using the impact theory of spectral line-shapes. The superimposed oscillations in the widths and shifts as functions of the Rydberg quantum number can be understood in terms of resonance electron-ground state atom scattering. The corresponding contributions to the spectra are determined by the energy and lifetime of a ³P autoionizing state of the negative alakali ion.     

Stark broadening of neutral helium lines

Using a semiclassical approach for the Stark broadening of atomic lines, we have calculated electron and proton impact line widths and shifts of 56 neutral He lines in the ultraviolet, visible and i.r. region of the spectrum. The comprehensive set of results obtained is used for investigation of Stark-broadening parameter regularities within the spectral series.     

Collisional broadening of infra-red absorption lines

The Lorentz half-widths of collision-broadened lines in the rotation-vibration bands of diatomic molecules vary with line number |m| in the P and R branches. The observed variation of half-width for lines in the 0 → 1 and 0 → 2 bands of CO and HCl are interpreted in terms of a simple fitting procedure. One dominant source of line broadening is assumed to consist of diabatic hard collisions involving transitions from each rotational level to all higher rotational levels; the effectiveness of this process, which varies from line to line, is described in terms of an empirically adjusted collision cross section, a maximum collision parameter related to independently measured molecular properties, and upon the availability of the required energy and angular momentum in molecular collisions. The second source of line broadening, assumed to be the same for all lines, includes all other types of collisions and is represented by a single empirically adjusted cross section. The simple fitting procedure is applied successfully to self-broadening of CO lines and to foreign-gas broadening of CO and HCl; for HCl self-broadening an additional cross section for resonant-dipole processes must be included. Possible applications of the fitting procedure to HBr, HF, and CO₂ are discussed. The simple procedure presented represents an approximation that may prove useful pending the development of readily applicable complete theories based on first principles.     

Stark broadening of neutral sodium lines

A semiclassical approach has been used to evaluate Stark broadening of atomic lines and also electron-and proton-impact line widths and shifts of 30 neutral sodium lines. The results are used to investigate Stark broadening-parameter regularities within the spectral series.     

Stark broadening of neutral potassium lines

Using a semiclassical approach, we have calculated electron-proton and Ar II impact line widths and shifts of 50 neutral potassium lines. The comprehensive set of results obtained is used for investigation of Stark-broadening-parameter regularities within the spectral series.     

Stark broadening of Y III spectral lines

Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line width and shifts for 32 Y III multiplets. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 476–481, July–August, 1998.     

Stark broadening of the Al resonance lines

Absolute Stark-broadened profiles of the Al resonance lines (3p-4s, γ = 3961.5 and 3944.0 Å) have been measured under conditions of complete LTE in a conventional shock-tube. Plasma electron densities were determined by using a laser-interferometer. Uncertainties in the measurements (15% for the widths and 13% for the shifts) are discussed. The results are compared with impact-broadening calculations.     

Stark broadening of ar VIII spectral lines

Using the semiclassical perturbation method, we consider, for nine Ar VIII transitions, widths and shifts of spectral lines that are due to collisions with electrons, protons, and ions of He III ut a perturbing particle density of 10¹⁸ cm⁻³ and temperatures between 200,000 and 3,000,000 K. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 286–288, May–June, 2000.     

Quasi-static ion broadening of isolated spectral lines

A tabulation of theoretical profiles of isolated spectral lines broadened by quasi-static ions is presented. This calculation is based on the quasi-static ion theory of Griem. A greater frequency range and a larger number of ion-broadening parameters than published by Griem are employed to facilitate comparisions with experiments. Observations on the validity of asymptotic wing formulas are included.     

Estimates of Stark broadening of oxygen ion lines

Recent measurements of spectral line widths for singly- and doubly-ionized oxygen atoms, are compared with the corresponding values predicted by the semi-empirical method of Griem. On the basis of these results, as well as a similar comparison for singly- and doubly-ionized nitrogen atoms in a recent paper, we propose some “experimental” values of the threshold Gaunt factors for these ions.     

Estimates of Stark broadening of nitrogen ion lines

Recent measurements of spectral line widths for singly- and doubly-ionized nitrogen atoms, are compared with the corresponding values predicted by the semi-empirical method of Griem. The overall agreement, for representative transitions from 6 multiples of N(II) and 3 multiplets of N(III), tends to confirm the usefulness and general validity of Griem's approach.     

Pressure broadening of millimeter lines of carbon monoxide

We report measurements on self-, N₂-, O₂-, and He-broadened widths of the 230-GHz line of carbon monoxide. The temperature dependence of the broadening parameters has been studied in the range 220–300 K. The results are compared with values previously obtained for the 115-GHz line and with published infrared data on the J = 1 ← 0 and J = 2 ← 1 transitions of carbon monoxide.     

Van der Waals broadening of argon absorption lines

Van der Waals broadening coefficients for Ar absorption lines have been measured using the resonant Faraday effect. These coefficients have the values of 2·9 ± 0·8, 2·4 ± 0·3, 1·9 ± 0·2 (in units of 10^?20 cm^?1 ?cm^?3) for the lines 6965 Å, 7067 Å, 7635 Å and 8115 Å, respectively, respectively. The measured coefficients are in reasonable agreement with measurements carried out on Ar emission lines and with theoretical calculations.     

Pressure broadening and shift of argon emission lines

Resonance and van der Waals broadening coefficients, as well as width to shift ratios, have been obtained by scanning argon emission lines produced in a high-pressure (～ 1 atm) glow discharge at a temperature of 1130°K. The resonance broadening coefficients yield absolute oscillator strengths of 0·283 ± 0·024 and 0·076 ± 0·008 for the two resonance lines at 1048 Å and 1067 Å. These oscillator strengths are in good agreement with previous measurements. The importance of higher-order terms in the van der Waals potential expansion is demonstrated by the measured coefficients.     

Stochastic broadening of signals in distorsionless transmission lines

The paper presents a theory of a stochastic continuous transmission line in which the series inductanceLΔ[1+l(x)], series resistanceRΔ[1+r(x)], shunt capacitanceCΔ[1+c(x)], and shunt conductanceGΔ[1+g(x)] are defined as Gaussian random functions. (The continuous line is considered as a limiting case of a lumped transmision line.) The non-negative random functionsL(x),R(x),C(x), andG(x) are chosen as delta-correlated, i.e. their correlation function is of the formΘδ(x′ −x″) whereΘ is a 4×4 positive definedx-independent matrix. Propagation of a signal of Gaussian shape is analyzed. A special attention is devoted to the so-called distorsionless lines defined by the deterministic conditionR/L=G/C. As a consequence of the stochasticity of the functionsl(x),r(x),c(x), andg(x), transmitted signals do become distorted: they become broadened. An explicit formula for this broadening is derived. This work has been supported by the Slovak Grant Agency VEGA under contract No. 1/4319/97.     

Impact broadening of alkali lines in brown dwarfs

Spectral line widths of the light alkalies are presented for conditions prevailing in brown dwarf atmospheres. A unified line shape theory and a set of pseudopotentials are used to compute widths of Li, Na, and K resonance lines perturbed by He and H₂. While limited available experimental data confirm the trends found in the theoretical values reported here, they suggest that improved potentials are needed.