Line Strengths and Transition Probabilities for the 2p^53p–2p^53s Transitions in Ne i

Computer-aided measurement of absorption line strengths from high resolution spectra greatly improves the accuracies to which relative line strengths can be determined. This article describes a computer program written for interactive use on a Prime minicomputer to fit simultaneously absorption line positions, strengths, linewidths, and continuum parameters. Application to the methane spectrum indicates that relative line strengths have been measured with accuracies of 2% or better for single isolated absorptions. Line strengths from the Q branches of the ν4 and ν1 + ν4 bands of methane are reported and compared to calculated values given in the 1980 Air Force Geophysical Laboratory (AFGL) Compilation of Molecular Parameters.

view Abstract Citations (191) References (103) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Late Emission from Supernovae: A Window on Stellar Nucleosynthesis Fransson, Claes ; Chevalier, Roger A. Abstract Observations of Type Ib and Type II supernovae show strong evidence that the energy input after 100-200 days is dominated by γ-rays from radioactive decay of ^56^Co. The energy deposition of these γ-rays, and the subsequent thermalization of the nonthermal electrons, are calculated using Monte Carlo techniques. The relative fractions going into heating, ionizations, and direct excitations are studied. Above an electron fraction of ~ 0.1 direct excitations are negligible, and the line emission arises from thermal processes. The temperature and ionization structure of the ejecta and its emission are discussed for general cases, and for detailed nucleosynthesis models. It is found that the emission is dominated by neutral and singly ionized lines, the strongest due to [O I], [Ca II], Mg I], [C I] and [Si I]. Tests of the explosion models and determinations of absolute and relative abundances from the late emission are studied. For a given model, the relative and absolute line strengths depend on both the column densities of the different abundance zones, and the relative abundances within each zone. For reliable modeling, the density structure must be known. It is shown how the emission-line profiles can be used as a powerful diagnostic of this, as well as of the abundance structure of the ejecta. The variation of the composition with the He core mass is shown to lead to substantial differences in the spectra, especially in the [O I]/[Ca II] emission-line ratio. Also, the degree of convective mixing is important for the result. The late spectrum is thus a good diagnostic of the nucleosynthetic structure of the supernova. At late times, a thermal instability is possible, since fine-structure far-IR lines dominate the cooling. This may trigger molecule and dust formation in the ejecta. The emission from a central pulsar may prevent this from occurring. The model is applied to the observations of the Type Ib SN 1985F. From a nebular analysis, including most of the diagnostic lines available, it is concluded that a white dwarf model cannot be excluded, purely on this basis. However, from calculations of the emission from 4-8 M_sun_ He cores, it is found that a core mass of ~ 8 M_sun_ reproduces both the total and the relative line strengths well, while lower mass cores give a considerably poorer agreement. Thus, the spectrum indicates that the Type Ib supernovae come from stars of ~ 25 M_sun_ and above. The density distribution, as inferred from the line profiles, is, however, considerably more extended than in the hydrodynamical models. This may be a result of instabilities. A macroscopic mixing of clumps from the different burning shells is shown to be the most likely explanation for the lack of a velocity correlation from lines of the different elements. Models based on exploding white dwarfs are shown to be inconsistent with the observations, owing to low absolute line luminosities and to the strong [C I] lines. Publication: The Astrophysical Journal Pub Date: August 1989 DOI: 10.1086/167707 Bibcode: 1989ApJ...343..323F Keywords: Cobalt Isotopes; Emission Spectra; Nuclear Astrophysics; Radioactive Decay; Supernovae; Line Spectra; Monte Carlo Method; Stellar Interiors; Astrophysics; GAMMA RAYS: GENERAL; NUCLEOSYNTHESIS; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS | data products NED (12) SIMBAD (7)

We have determined the absolute transition probabilities of 27 emission lines of neutral argon originating from the 3p54p→3p54s transition array in the wavelength region from 650 to 1100 nm using an argon-filled hollow cathode discharge lamp. The absolute transition probabilities have been deduced using the lifetimes of the upper levels and the measured branching fractions. Atomic oscillator strengths and relative line strengths for all the transitions have been computed using calculated transition probabilities. The experimentally determined transition probabilities are found to be in good agreement with that calculated in the intermediate coupling (IC) scheme. The comparison of experimentally determined transition probabilities with reported theoretical transition probabilities confirms that the IC scheme for the lower as well as for the upper levels seems to be a useful scheme for the level designation for the 3p54p to 3p54s configuration-based levels in argon. Furthermore, the measured relative line strengths are used to validate the J-file sum rule for the 3p54p→3p54s transition array of argon. The reported transition probabilities, oscillator strengths, and relative line strengths are compared with the published data, showing good agreement.

A method is described for calculating the relative absorption oscillator strengths of spectral lines of an element from the gradients of their working curves in emission spectral analysis. A mathematical expression for the gradient of the working curve is derived taking into account the atomic self- absorption of the spectral lines in the cooler region of the discharge and assuming a Doppler broadening line profile for both emission and self-absorption. Local thermal equilibrium is assumed in the absorption region in the arc fringe, and the principle of detailed balance is applied to that region for evaluating the relative population of the lower excited states of the atoms. Correlation between theory and published experimental results for the average gradient of the working curves for 14 lines of Fe I lead to calculation of their relative oscillator strengths as well as to some informations of the average temperatures of the emission and absorption regions. The good agreement between the calculated gf values and those determined by other investigators emphasizes the validity of the assumption of local thermal equilibrium in the arc fringe.

Relative line strengths for s-p, p-d, and d-f transitions of Ne, A, Kr, and Xe are derived by the method of Koster and Statz, under the assumption of the j-l coupling scheme of Racah. When the relative strengths are given a common denominator, a set of rules for strong lines becomes apparent, similar to rules which have been noted for L-S coupling. For comparison with experiment, we consider several sets of Ne lines, each set having one specific initial, and one final configuration. For the higher l values (p-d and d-f) the lines found to give oscillation are almost exclusively the lines with large relative strengths. The absolute line strengths S are then calculated in the Coulomb approximation of Bates and Damgaard; we consider only transitions between two excited states. There is the following simple relation between (gain constant/volume density of inversion) and S:α/(N2/g2−N1/ g1)=1.76×10−13 (mass number)1/2S. The units of α are cm−1. N1 and N2 are in cm−3. S is in atomic units, a02e2. The linewidth is taken to be determined by Doppler broadening at 400°K. For several lines upon which measurements of α have been made, we give the corresponding values of (N2/g2−N1/g1). This inversion quantity is a population difference between elementary quantum states.

view Abstract Citations (5) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Relative Strengths of Spectral Lines with Mixed Vector Couplings: Dipole Transitions between LS and Other Couplings Escalante, V. ; Gongora-T., A. Abstract The relative strength of spectral lines of electric dipole transitions is calculated in which one of the states is described with the LS coupling scheme and the other is described with the LK, j-K, or j-j coupling scheme. Selection rules for each type of transition are described. As examples, tables are given for transitions of the type 2P nl - 2P m(l-prime) for 1 = l or less, l-prime = 4 or less, and any n and m for the LS-LK and LS-j-K cases. The results can be compared with observed relative intensities of optically thin spectral lines between states with similar quantum numbers. As examples, the results for transitions in the array 3d-4f of N II are compared with observations of planetary nebulae. Publication: The Astrophysical Journal Supplement Series Pub Date: November 1990 DOI: 10.1086/191519 Bibcode: 1990ApJS...74..819E Keywords: Electric Dipoles; Heavy Elements; Line Spectra; Planetary Nebulae; Transition Probabilities; Optical Thickness; Quantum Numbers; Astrophysics; ATOMIC PROCESSES; NEBULAE: PLANETARY; TRANSITION RATES full text sources ADS | data products SIMBAD (2)

With a high-current wall-stabilized arc, operated in helium with small admixtures of CO2, relative line strengths for some prominent infrared multiplets of neutral carbon have been measured. The results are analyzed in conjunction with previously obtained experimental data in the visible and near infrared region of the spectrum. Our experimental results are compared with those resulting from the Russell-Saunders coupling scheme and with recent sophisticated intermediate coupling calculations. The results of this paper may be helpful for the improvement of atomic structure codes used for line strength calculations. The determined relative line strengths may also be useful in astrophysical applications.

In a wall-stabilized cascade arc helium plasma with some traces of SF6 has been generated. On the basis of measured total line intensities emitted from the plasma, the relative line strengths within twelve multiplets of neutral sulfur (SI) have been determined. The studied lines cover the spectral range from 415 nm to 1046 nm. The obtained experimental line strengths are compared with results of recent theoretical data as well as with results of older experiments. In addition the SI line strength data are compared with analogous transitions in the OI spectrum.

Relative line strengths have been computed for the transition arrays of 3p54s–3p54p and 3p54s–3p55p in Ar i. Intermediate-coupling theory has been used, starting from LS coupling, and using the experimental energy levels as data for determining the parameters of the theory by least-squares adjustment of the calculated energies. The results have been placed on an absolute scale using the Coulomb approximation. The Lande g factors computed agree well with the observed values. The calculated transition probabilities are in fairly satisfactory agreement with various experimental determinations, and this agreement is better than that obtained using either LS- or jl-coupling calculations. The results for the 4s–4p array appear to be more accurate than those for the 4s–5p array.

Measurements of relative line strengths in N I multiplets for transition arrays 3s– np ( n=3, 4, 5)

The transition array for the transitions between the configurations (3d 3 + 3d 24s) and 3d 24p in Ti ii are presented here. The relative line strengths have been calculated in the intermediate coupling scheme, taking into account interaction between configurations. The relative phase and magnitude of the radial transition integrals (s-p) and (d-p) for the jumping electron in the LS coupling have been determined empirically.

Nonadiabatic effects in the B, C and E, F states of HD

We have studied Raman transitions between vibrational levels of atoms confined in the antinodes of a two-dimensional (2D) optical standing wave by means of dipole forces. These transitions are excited by the cooperation of the confining 2D field, with a weak probe laser beam directed through the atomic sample. We experimentally find that the relative line strengths corresponding to transitions from the vibrational ground state to the first and second excited states depend on the polarization of the probe beam. The excitation mechanism is based on a time-modulated distortion of the potential wells. We discuss how the spatial geometry of this distortion depends on the probe polarization, thus qualitatively explaining the experimental observations.

We present recent observations from the Hubble Space Telescope-Cosmic Origins Spectrograph aimed at characterizing the auroral emission from the extrasolar planet HD 209458b. We obtained medium-resolution (R ∼ 20,000) far-ultraviolet (1150–1700 Å) spectra at both the Phase 0.25 and Phase 0.75 quadrature positions as well as a stellar baseline measurement at secondary eclipse. This analysis includes a catalog of stellar emission lines and a star-subtracted spectrum of the planet. We present an emission model for planetary H2 emission, and compare this model to the planetary spectrum. No unambiguously identifiable atomic or molecular features are detected, and upper limits are presented for auroral/dayglow line strengths. An orbital velocity cross-correlation analysis finds a statistically significant (3.8σ) feature at +15(± 20) km s−1 in the rest frame of the planet, at λ1582 Å. This feature is consistent with emission from H2 B–X (2–9) P(4) (λrest = 1581.11 Å); however, the physical mechanism required to excite this transition is unclear. We compare limits on relative line strengths seen in the exoplanet spectrum with models of ultraviolet fluorescence to constrain the atmospheric column density of neutral hydrogen between the star and the planetary surface. These results support models of short-period extrasolar giant planets with weak magnetic fields and extended atomic atmospheres.

view Abstract Citations (42) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS On Some Predicted and Observed Features of Quasi-Stellar Sources Bahcall, John N. Abstract Some observed features of quasi-stellar sources are correlated in a way that enables one to predict with simple models the relative strengths of the Lyman lines and the optical depth of the nebulae beyond the Lyman continuum. The relative strengths of the Lyman lines are calculated first for an optically thin nebula, and then expressions are derived for the amount by which the intensities of the more energetic Lyman lines are attenuated in an optically thick nebula. The probability that resonant radiation escapes from an optically thick nebula is estimated with a diffusion equation and is found to be much larger than previously estimated if some emission originates near the surface of the nebula. Three possible causes for the observed emission widths are discussed, and it is concluded that the most likely cause is random motions of gas clumps or filaments. A suggestion due to Schmidt for constructing models of quasi-stellar sources that are optically thin to electron scattering is developed quantitatively. The average degree of ionization of the hydrogen in a quasi-stellar source and the optical depth beyond the Lyman continuum are expressed in terms of the unknown ionizing flux. A plausible guess for the strength of the ionizing flux indicates that some quasi-stellar sources may be optically thin beyond the Lyman continuum. A possible correlation is suggested between the age (and luminosity) of the nebula of a quasi-stellar source and the value of its optical depth beyond the Lyman continuum. Several other observational consequences of our discussion are also described. In particular the predictions are shown to depend sensitively on whether or not quasi-stellar sources are, like the nuclei of Seyfert galaxies, surrounded by an appreciable amount of neutral hydrogen. Publication: The Astrophysical Journal Pub Date: September 1966 DOI: 10.1086/148815 Bibcode: 1966ApJ...145..684B full text sources ADS |