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In this paper we emphasize the non-Lorentzian behavior of the Balmer series in helium-dominated DBA white dwarf stars for which the decades-old problem exists for the determination of the hydrogen abundance. In a very recent work, we have shown that quasi-molecular line satellites due to H-He and H-H collisions are responsible for the asymmetrical shape of the Lyman-alpha lines observed with the Cosmic Origin Spectrograph (COS) and that a similar asymmetry exists for the Balmer-alpha line profiles. In continuation with very recent work, where the n=2, 3 potential energies and transition dipole moments from the ground state were determined, here, we present accurate H-He potential energies and electronic transition dipole moments concerning the molecular states correlated with H(n=4)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-beta line of H perturbed by He. Because of the general trend characterizing the repulsive Sigma states of the potential energies involved in the Balmer series, the amplitude in the core of the line is decreasing very fast with the order of the series when the helium density gets as large as 10^21 cm^-3. This study is undertaken by applying a unified theory of spectral line broadening that is valid at very high helium densities found in DZA white dwarf stars. The treatment includes collision-induced (CI) line satellites due to asymptotically forbidden transitions, and it explains the asymmetry observed in their spectra., 7pages, 8 figures. arXiv admin note: text overlap with arXiv:2201.00878

Kossakowski, D., et al., We present the discovery of a transiting mini-Neptune around TOI-1201, a relatively bright and moderately young early M dwarf (J ≈ 9.5 mag, ~600-800 Myr) in an equal-mass ~8 arcsecond-wide binary system, using data from the Transiting Exoplanet Survey Satellite, along with follow-up transit observations. With an orbital period of 2.49 d, TOI-1201 b is a warm mini-Neptune with a radius of Rb = 2.415 ± 0.090 R⊕. This signal is also present in the precise radial velocity measurements from CARMENES, confirming the existence of the planet and providing a planetary mass of Mb = 6.28 ± 0.88 M⊕ and, thus, an estimated bulk density of 2.45-0.42+0.48 g cm-3. The spectroscopic observations additionally show evidence of a signal with a period of 19 d and a long periodic variation of undetermined origin. In combination with ground-based photometric monitoring from WASP-South and ASAS-SN, we attribute the 19 d signal to the stellar rotation period (Prot = 19-23 d), although we cannot rule out that the variation seen in photometry belongs to the visually close binary companion. We calculate precise stellar parameters for both TOI-1201 and its companion. The transiting planet is anexcellent target for atmosphere characterization (the transmission spectroscopy metric is 97-16+21) with the upcoming James Webb Space Telescope. It is also feasible to measure its spin-orbit alignment via the Rossiter-McLaughlin effect using current state-of-the-art spectrographs with submeter per second radial velocity precision., Part of this work was supported by the German Deutsche Forschungsgemeinschaft (DFG) project number Ts 17/2–1. CARMENES is an instrument at the Centro Astronómico Hispano-Alemán (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Junta de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Científicas (CSIC), the Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg,Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. This work was based on data from the CARMENES data archive at CAB (CSIC-INTA). We acknowledgefinancial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4]/AEI/10.13039/501100011033 and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Instituto de Astrofísica de Canarias (SEV-2015-0548), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737), the European Research Council under the Horizon 2020 Framework Program (ERC Advanced Grant Origins 83 24 28), the Generalitat de Catalunya/CERCA programme, the DFG priority program SPP 1992 “Exploring the Diversity of Extrasolar Planets (JE 701/5-1)”, the European Research Council under the Horizon 2020 Framework Program via ERC Advanced Grant Origins 832428 and under Marie Skłodowska-Curie grant 895525.

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An exact quantum adiabatic evaluation of the shift of an isolated spectral line is applied to the potassium 7s-4p transition perturbed by argon. The long-range interaction of excited alkali states with noble gases is computed with a large basis set of unperturbed atomic states, a multipole interaction and a pseudopotential to compare with a measurement of the dependence of the shift on temperature. The parameters of the theoretical potassium-argon excited-state potential are determined by adjusting the theoretical temperature dependence to fit the observations. Previous pseudopotential models, fitted to ground-state interactions derived from scattering experiments, show weaker long-range interactions than the authors find. The conclusions are consistent with independent line wing experiments on this and other alkali-noble-gas systems that reveal significant interactions at long range.

A small fraction of the DA white dwarf are known to have rather low effective temperature. It is of considerable interest to determine line profiles in these extreme physical conditions. In such cool white dwarfs the perturber density is so high that the one perturber approximation breaks down and the collisional effects must be treated by using the autocorrelation formalism in order to take account the simultaneous collisions with more than one perturbing atom.

International audience; The optical spectra of L- and T-type dwarfs exhibit a continuum dominated by the far wings of the absorption profiles of the Na 3s-3p and K 4s-4p doublet perturbed by molecular hydrogen and helium. We report on our work on new calculations of line profiles of Na and K perturbed by He for the conditions prevailing in brown dwarf atmospheres and very cool white dwarfs.

Complete spectral‐line shapes were computed for a modeled Ar‐perturbed K spectral line in the impact approximation and in the non‐impact regime. Morse potentials were used instead of more representative K/Ar pseudo‐potentials because of computation‐time restrictions. Our model consisted of an upper initial state characterized by a Morse potential with a depth of 100 cm−1, and a lower final state characterized by a zero potential. The reduced mass was that of the K/Ar system. The theory was based on the non‐impact derivation of Baranger [1]. We expanded his results for convenient manipulation in the computation. Three important aspects of our work were: the wave functions were expanded in terms of partial waves; initial conditions were devised for the solutions of the Schrodinger equations; a change was made in our programming for the evaluation of an important matrix expression which had a significant effect on the onset pressure of the non‐impact regime. We found for these short‐range Morse potentials th...

A laser‐produced plasma in hydrogen is being used to study the shift, shape and width of the Balmer α and Lyman β spectral lines emitted by the n = 3 state of atomic hydrogen perturbed by H+ and electrons. Recent measurements at densities up to 1020 cm−3 show that the Balmer α center shifts monotonically to the red with increasing density. The largest shifts seen, of the order of 200 A, occur with shift‐to‐width ratios of up to 0.25. At densities below 1019 cm−3 the shift‐to‐width ratio is an order of magnitude smaller, in agreement with published gas‐liner pinch plasma experiments, but the laser‐plasma explores an order of magnitude higher density. The broad core profiles are consistent with unified line shape theory calculations based on exact H2+ potentials. Balmer α exhibits satellites, some of which are close to the unperturbed line center, and are expected to influence the shift and shape of the line at high H+ density. The satellites may influence the line shift at the highest densities observed. L...

The equations for a general quantum-mechanical theory for the perturbation shift and broadening of spectral lines in the non-impact regime have been numerically solved for a pseudo-potential of the Na/Ar system in the 3s S state. Spectral line shapes have been shown for low and high pressures (P). The variation with P of the linewidths for the non-impact regime and for the impact approximation is depicted in the range P=0.5−20 torr.

The low energy interactions of neutral and ionized hydrogen atoms are fundamental processes which also have important applications to the diagnostics of laboratory and astrophysical plasmas. Satellites in the far wings of Lyman α and Lyman β have been identified as ultraviolet absorption features in the spectra of white dwarf and λ Bootis stars, and they are seen in the emission spectra of plasmas produced when a pulsed laser excites a target H2 gas. The observed Lyman series profiles agree with unified line shape theory which includes variation of the dipole transition moment during the radiative collision.

A general quantum-mechanical theory of the perturbation shift and broadening of spectral lines in the non-impact regime has been extended and programmed and applied to two simple potentials—the square-well potential and a Morse potential. At low pressure, the non-impact and impact line shapes coincide, whereas at high pressures the non-impact line has acquired an asymmetry, a slight relative shift, and a width about twice that of the impact line.

A reliable determination of the line profiles of atomic hydrogen for physical conditions of cool white dwarfs requires a unified theory which takes into account both the singlet and triplet transitions contributing to Lyman alpha using accurate interaction potentials and radiative dipole transition moments. We show that multiple perturber effects have to be considered using the autocorrelation formalism. A comparison with experimental laboratory spectra of cool dense plamas also shows that indeed multiple H-perturbers are an important influence in the far wing extending to 3000 A in the ultraviolet. Under cool dense white dwarf atmosphere conditions, multiple perturber collisions for the singlet states contribute more to the ultraviolet opacity than binary collisions of the triplet states.

The shift of an isolated spectral line broadened by collisions is calculated by an exact, quantum, adiabatic theory. The potential is based on Baylis’1 use of pseudopotentials, expanded here with a larger basis set and with two adjustable parameters. Results are applied to measurements of the shift of a potassium spectral line for the 7s→4p transition perturbed by argon. The two parameters are adjusted to fit computed shifts to experimental data from 450 to 760 K.

The impact broadening and shift of the sodium resonance lines by noble gases have been redetermined with improved instrumentation and data reduction allowing for asymmetries. An increase of width, shift and asymmetry with the heavy noble gases is noted, as is a D2 to D1 width ratio greater than one for helium and neon, but less than one for argon, krypton and xenon. Comparisons are drawn with different published calculations to show that the widths are accounted for by the Pascale-Vandeplanque potential whether with a fully quantal or a semiclassical impact broadening theory. On the other hand, the Nikitin-Roueff potential does not work well in this case. Available calculations of the shift are less satisfactory and no predictions of the observed asymmetries have been made.

Multiple satellites appear in absorption spectra on both components of the Cs $6s\ensuremath{-}9p$ doublet perturbed by xenon at densities of the order of ${10}^{19}$ atoms/${\mathrm{cm}}^{3}$. The profiles of these perturbed lines computed with the Anderson-Talman theory, and the density dependence of the absorption at the multiple satellite frequencies, definitely identify the origin of the satellites as the combined additive effect of one to four perturbers.

The 6s-7p, 8p and 9p absorption transitions in caesium perturbed by xenon foreign gas at a temperature of approximately 500K and densities up to 1.2*1019 atoms/cm3 have been observed with a high-resolution computer-controlled spectrometer. A Fourier analysis technique to deconvolve the asymmetric line core from instrumental and Doppler effects yields width, shift and asymmetry for the 7p an 8p doublets independent of the instrument and directly comparable with line-broadening calculations. Normalised profiles of the wings of the 7p and 8p transitions, and of the entire 9p contour are also given from measurements at sufficiently high resolution that instrumental effects are negligible. The observed line core-parameters and line profiles are compared with Anderson-Talman lineshape calculations (1956). The authors also note the observation of multiple-perturber satellites as predicted by the Anderson-Talman theory based on the assumption of additivity of the interaction.

The collision broadening and shift of lithium, sodium, potassium, rubidium and caesium principal series lines by helium, neon, argon, krypton and xenon perturbers is tabulated based on the impact approximation and semiempirical interatomic potentials. Comparisons are made with available experimental data. The temperature dependence of the line broadening and shift rates is also estimated.

New measurements of satellites of mercury spectral lines in the presence of argon, krypton, and xenon are reported. While a few satellites appear on some lines, not all lines show distiguishable intensity maxima in the continuum adjacent to the pressure broadened line. Features previously reported in the case of the 2536 A resonance line are confirmed for argon and krypton. New results are reported for xenon. In addition, detailed measurements of the Hg–Ar, Hg–Kr, and Hg–Xe vibrational spectra that appear near 2536 A are reported and partially analyzed. Evidence pointing to the origin of the 2536 A violet satellites as due to collisions between free atoms rather than bound pairs is also discussed.

A semiempirical calculation of alkali‐noble gas interatomic potentials applicable to excited states of the alkali at internuclear separations and energies important for the interpretation of optical line broadening experiments is presented. The assignment of a single adjustable parameter is based on a comparison with scattering cross‐section measurements of ground state potentials. Evidence that the repulsive interaction scales as the collision cross section of the noble gas atoms for low energy electrons is presented, and simple formulas are developed to predict potentials for all alkali‐noble gas combinations as a function of noble gas dipole and quadrupole polarizabilities and alkali unperturbed energy. Additional comparisons are made with data from satellite bands in Cs–Xe and Cs–Kr spectra, and the impact broadening and shift of alkali spectral lines at low foreign gas pressure is calculated from the predicted potentials and compared with available experimental data.

The problem of computing the shape of an atomic spectral line perturbed by neutral atom collisions is considered and a precise numerical evaluation of the exact semiclassical line shape for a selected variety of potentials, temperatures and gas densities is reported. The need for relatively high numerical accuracy in the evaluation of the correlation function is stressed and the generation of spurious oscillations in the spectral line wing due to numerical error is illustrated. An accurate evaluation shows an absence of rapid oscillations and reveals a satellite very similar but not identical in shape to the satellites predicted with a JWKB approximation for a simple potential well. The general features of the computed line wings agree with available observations. Dynamical smearing of the classical static singularity in the line wing is an important process. Only potentials with constant depth over long range have been found to produce very sharp satellites, while the usual potential wells produce simple shoulders on the spectral line wings. The possible application of this computational technique for the evaluation of excited-atom-neutral-perturber potentials from spectral line data is also considered.

Observation of the time‐dependence of excitation transfer between Cs 7p 2P1/2 and 2P3/2 levels caused by collisions with xenon are reported. The 2P levels were selectively excited with an N2 laser‐pumped dye laser, and the spectrum of the fluorescence radiation was observed with 5 nsec time resolution. The lifetimes of the levels were found to be (2P1/2) 154±2 nsec and (2P3/2) 135±2 nsec, and the 2P1/2 to 2P3/2 transfer cross section at 325±10 °K is 0.150±0.002 A2. An analysis of the time‐dependent decay versus xenon partial pressure shows that the cross section for quenching or collision induced radiation is less than 4×10−3 A2. This demonstrates that collision induced transitions cannot be important in the formation of near red satellites on the Cs 6s–7p lines perturbed by Xe. In addition, the radiative decay constant for the satellite is identical to that for the line within experimental uncertainty. The correspondence of satellite and line decay curves provides a method of identifying satellites with ...

Observations are reported of the collision broadening and shift of the hydrogen‐α line by helium, neon, and argon foreign gases. An analysis of the line profile from a microwave‐excited discharge with allowance for Doppler broadening and fine structure yields the effect of foreign gas pressure on the spectral line shape. The classical theory of spectral line impact broadening together with an interatomic potential proposed previously for alkali–noble gas interactions correctly predicts the observed broadening and shift of the line.

Emission spectra, wavelengths and photoelectric intensities of triply-ionized gadolinium, using hollow cathode source with Czerny-Turner vacuum spectrograph