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Results for “OSCILLATOR STRENGTHS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

High-resolution oscillator strength measurements for the A(v') - X(0) bands of carbon monoxide with 11 less than or equal to v' less than or equal to 14

Band oscillator strengths (f-values) for four bands of the Fourth Positive system (A (1)Pi - Chi(sup 1) Sigma(+)) of CO have been determined from high-resolution (lambda/Delta lambda approximately equal to 150,000) absorption spectra. The bands, (14, 0) through (11, 0), are at wavelengths between 121 and 127 nm. Our f-values for the (11, 0) and (12, 0) bands support those of Chan, Cooper, & Brion (1993), which have been shown to be consistent with observations of CO in the clouds in the line of sight to zeta Oph. Our f-values for the (13, 0) and (14, 0) bands are the first directly measured values for these bands.

Smith, Peter L.↗
NASA NTRS1973

Oscillator strengths of ultraviolet Fe I lines from hook-method measurements on a furnace

The hook method, which makes use of anomalous dispersion, was employed to measure 107 absolute oscillator strengths of Fe I on a high-temperature furnace. The absolute scale was established before and after each run by recording the anomalous dispersion near a strong resonance line with accurately known f-value. The results cover three lines with wavelengths from 1934 to 1941 A, and 104 lines lying between 2084 and 3194 A - mostly transitions originating from the a 5 D ground state. The average error of the f-values is plus or minus 20%, and the largest and smallest errors given are plus or minus 10 and plus or minus 60%. Disagreements exceeding an order of magnitude are found with previous values in the literature.

Banfield, F. P.↗
NASA NTRS1981

Measurement of the oscillator strengths and autoionization widths of the neutral-aluminum multiplet 3s2 3p2 P0 - 3s 3p2 2P

The hook method is used in conjunction with absorption equivalent width measurements to determine the oscillator strengths and line widths of the Al I multiplet 3s2 3p2 P0 - 3s 3p2 2P at 176 nm. Autoionization is found to be the dominant decay channel for the two levels of the 3p2 2P term, with autoionizing widths of 4.0 and 0.87 x 10 to the 10th/sec for J of 3/2 and 1/2, respectively. The van der Waals scattering cross section for the Al I transition at 176.91 nm by He is determined to be (1.3 + or - 0.3) x 10 to the -14th sq cm at 2400 K, and a solar spectrum calculation centered at 176 nm shows that the Al I features are possible diagnostic probes of (1) solar non-LTE processes, and (2) the temperature minimum and structure of the lower chromosphere.

Lombardi, G. G.↗
NASA NTRS1989

Oscillator strengths and electron collisional excitation cross sections for atomic oxygen

The electron-impact excitations of 12 states of O I are analyzed using a close-coupling approximation. The absorption oscillator strengths for dipole-allowed transitions among the states are calculated. Cross sections for excitation of the states by electron impact in the energy region 13.87 to 100 eV are compared with the data of Smith (1976) and Doering and Gulcicek. It is observed that there is a correlation between the data at energies 13.87, 20, and 30 eV for the (3)P-3p(5)P transition and at energies 13.87 and 16.5 eV for the (3)P-3s(5)S(0) transitions; however, for the dipole-allowed (3)P-3d(3)D(0) and (3)P-3s(prime)(3)D(0) transitions there are discrepancies in magnitude.

Tayal, S. S.↗
NASA NTRS2020

High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem

For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic 2p - 3d transitions, 3C and 3D, in Fe XVII ions found oscillator strength rations f(3C)/f(3D) disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lines using synchrotron radiation at PETRA III, and reach, at a millionfold lower photon intensities, a 10 times higher spectral resolution, and 3 times smaller uncertainty than earlier work. Our final result of f(3C)/f(3D) = 3.09(8)(6) supports many of the earlier clean astrophysical and laboratory observations, while departing by five sigmas from our own newest large-scale ab initio calculations, and excluding all proposed explanations, including those invoking nonlinear effects and population transfers.

Electron-ion collisions↗
NASA NTRS1972

Radiative lifetimes and absolute oscillator strengths for the SiO A/super 1/Pi to X/super 1/Sigma+ transition.

Measurement of a radiative lifetime of 9.6 (plus or minus 1.0) nsec for the SiO A(super 1)Pi state is reported. RKR Franck-Condon factors have been computed and, with these, absolute oscillator strengths are calculated. A band system at 3022 A has been found that may be due to SiO+, but the band is not resolved at our experimental resolution, and identification remains uncertain. The upper state of the carrier of this spectrum has a radiative lifetime of 8.3 (plus or minus 0.8) nsec.

Smith, W. H.↗
NASA NTRS1984

The depletion of pre-interstellar matter and an examination of Ni II oscillator strengths

IUE absorption-line data obtained at 110-320 nm with resolution 10-30 pm toward the B-star component of the multiple system of Alpha Sco are presented in graphs and tables and used to characterize the circumstellar shell around the M1.5 Iab component. Resonant lines of Ni II are identified at strengths in excess of 4 pm and fit to a growth curve constructed using the Fe II, Si II, and Mn II lines, and the results are found to confirm the oscillator strengths determined by Kurucz and Peytremann (1975) to within 50 percent. Shell depletions 2-20 times smaller than those for dense clouds such as the surrounding Oph complex are calculated and attributed to the formation of circumstellar dust. The implications of the results for the condensation of various elements in dense and diffuse clouds are explored.

Cardelli, J. A.↗
NASA NTRS1992

Absorption band oscillator strengths of N2 transitions between 95.8 and 99.4 nm

Molecular nitrogen plays a central role in the energetics of the earth's upper atmosphere and is the major constituent of the atmospheres of the planetary satellites Titan and Triton. This paper reports a new set of absorption oscillator strengths measured at higher resolution for seven bands in the 95.8-99.4 nm region. The results are compared with earlier, lower resolution absorption measurements, electron scattering measurements, and calculations based on a deperturbation analysis of the excited states.

Stark, G.↗
NASA NTRS1980

Oscillator strength trends in group IV homologous ions

Shock-tube data are used to examine systematic f-value behavior in prominent visible transition arrays for the homologous emitter sequence Si-II, Ge-II, Sn-II, and Pb-II. Regularities found in these data are compared with trends in lighter elements. Agreements and disparities with theoretical and experimental oscillator strengths from existing literature are noted.

Miller, M. H.↗
DOE OSTI2026

Determination of Oscillator Strength of CdSe Nanoplatelets from Strong Light-Matter Coupling

We report exciton-polaritons formed from core-only, core-crown, and core-shell NPLs, which, alongside finite-difference time-domain (FDTD) simulations of Fabry-Pérot cavity mode volume, allow for the verification of core-only and determination of core-crown and core-shell oscillator strengths. Additionally, we show that polaritons can be used not only as a means of altering the properties of coupled emitters, but as an analytical tool to better understand the properties of coupled emitters.

Hancock, Benjamin↗
NASA NTRS1988

Differential oscillator strengths and dipole polarizabilities for transitions of the helium sequence

The dipole radial integral for an initial discrete 1s state and a final continuum state has been calculated under the screened hydrogenic model. In this model, single-electron hydrogenic wave functions are employed, and the initial and the final states are treated by two different effective-charge parameters. Numerical values of differential oscillator strengths for transitions from 1s2 1S to the continuum for the helium sequence ions are obtained. Also calculated are the dipole polarizabilities, which are found to be in excellent agreement with the results of other authors.

Khan, F.↗
NASA NTRS1978

Oscillator strength trends in group IVb homologous ions

Shock tube data are used to examine the systematic f value behavior in prominent visible transition arrays (ns-np, np-(n+l)s, np-nd) for the homologous emitter sequence Si 11, Ge 11, Sn 11, and Pb 11. Regularities found for these data are compared with trends in lighter elements. Agreements and s disparities with theoretical and experimental oscillator strengths from the literature are noted.

Miller, M. H.↗
NASA NTRS1993

The International Colloquium on Atomic Spectra and Oscillator Strengths for Astrophysical and Laboratory Plasmas

This was the fourth in a series of colloquia begun at the University of Lund, Sweden in 1983 and subsequently held in Toledo, Ohio and Amsterdam, The Netherlands. The purpose of these meetings is to provide an international forum for communication between major users of atomic spectroscopic data and the providers of these data. These data include atomic wavelengths, line shapes, energy levels, lifetimes, and oscillator strengths. Speakers were selected from a wide variety of disciplines including astrophysics, laboratory plasma research, spectrochemistry, and theoretical and experimental atomic physics.

Sugar, J.↗
NASA NTRS1974

Oscillator strengths for neutral sodium and the interstellar sodium abundance in zeta Ophiuchi

Use of the high-frequency deflection technique to measure radiative lifetimes for the 4p and 5p upper states in Na I, along with relative populations of a number of ns and nd states. These data have been used to obtain f-values for the corresponding resonance transitions in Na I, which proved to be in reasonable agreement with previous oscillator strengths. From the theoretical curve of growth for pure Doppler broadening, revised line ratios for D1/3303 are given and are compared with observations of Na I in zeta Oph.

Erman, P.↗
NASA NTRS1993

Oscillator strengths of the Si II 181 nanometer resonance multiplet

We report Si II experimental log (gf)-values of -2.38(4) for the 180.801 nm line, of -2.18(4) for the 181.693 nm line, and of -3.29(5) for the 181.745 nm line, where the number in parentheses is the uncertainty in the last digit. The overall uncertainties (about 10 percent) include the 1 sigma random uncertainty (about 6 percent) and an estimate of the systematic uncertainty. The oscillator strengths are determined by combining branching fractions and radiative lifetimes. The branching fractions are measured using standard spectroradiometry on an optically thin source; the radiative lifetimes are measured using time-resolved laser-induced fluorescence.

Bergeson, S. D.↗