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Seely, J. F.

Publications and source records attributed to Seely, J. F..

34 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Measurement of wavelengths and lamb shifts for inner-shell transitions in Fe XVIII-XXIV

The wavelengths of inner-shell 1s-2p transitions in the ions Fe XVIII-XXIV have been measured in solar flare spectra recorded by the Naval Research Laboratory crystal spectrometer (SOLFLEX) on the Air Force P78-1 spacecraft. The measurements are compared with previous measurements and with recently calculated wavelengths. It is found that the measured wavelengths are systematically larger than the wavelengths calculated using the Z-expansion method by up to 0.65 mA. For the more highly charged ions, these differences can be attributed to the QED contributions to the transition energies that are not included in the Z-expansion calculations.

Seely, J. F.↗
NASA NTRS1986

Spectrum of sodiumlike selenium - Se XXIV

High-resolution spectra of Se XXIV have been obtained with a 3-m grazing-incidence spectrograph. Thin plastic foils coated with selenium were irradiated with four or eight beams of the OMEGA laser in a line-focus configuration. Spectrograms were obtained by viewing the plasma axially. Prominent in the spectra were the 3s-3p and 3p-3d transitions in the 150-240-A region and the transitions nl-(n + 1)l-prime with n = 3, 4 in the 24-80-A region. The energy levels and ionization limit derived from the measured wavelengths are also presented.

Brown, C. M.↗
NASA NTRS1986

Measured wavelengths for n = 4 to 2 transitions in Fe XXIV and Fe XXIII

Accurate wavelength measurements for Fe XXIV and Fe XXIII transitions near 8 A and of the type N = 4 to 2 from solar spectra are presented. The resonance transition in the hydrogenlike ion Mg XII is used as a reference. The measured wavelengths are compared with previous ones and with ab initio and semiempirical calculations that include screening parameters in the nonrelativistic, relativistic, and radiative terms.

Seely, J. F.↗
NASA NTRS1985

High-resolution observations of X-ray transitions in Fe XXV-XXIII

The wavelengths of X-ray transitions in Fe XXV-XXIII have been measured using a high-resolution spectrum reflected from the Ge(13-1) planes. A number of transitions have been resolved for the first time in solar flare spectra, and the contributions of the Fe XXIV n = 3 satellites to the Fe XXV parent lines are discussed. The QED contributions to the wavelengths of the Fe XXIV n = 3 satellite transitions have been determined.

Seely, J. F.↗
NASA NTRS1985

Density sensitive X-ray line ratios in the Be I, B I, and Ne I isoelectronic sequences

The intensities of X-ray transitions in highly charged ions in the Be I, B I, and Ne I isoelectronic sequences have been calculated as functions of electron density. The intensities of the transitions from the 2s(n)2p(m)3p configuration, relative to the intensities from the 2s(n)2p(m)3s and 2s(n)p(m)3d configurations, are strong functions of electron density in high-density plasmas. The density sensitivity occurs at electron densities between 10 to the 16th/cu cm (for Si ions) and 10 to the 22nd/cu cm (for Kr ions). Opacity is unimportant for plasma dimensions that are characteristic of dense laser-produced plasmas. These X-ray line ratios represent a promising new density diagnostic for high-density plasmas.

Feldman, U.↗
NASA NTRS1985

Electron temperature and average density in spherical laser-produced plasmas - Ultraviolet plasma spectroscopy

The average values of the electron temperature Te and the electron density Ne in the corona plasmas of spherically irradiated high-Z targets have been estimated. Targets composed of the elements Cu through Br, Rb, and Mo were irradiated using the fundamental (1.06 microns) and the frequency-tripled (351 nm) output of the Omega laser system. Spectra were recorded in the wavelength region 15-200 A. Using various extreme ultraviolet spectroscopic techniques, it is found that for the case of a Mo plasma produced by frequency-tripled laser irradiation, Te = 2600 + or - 600 eV and Ne is greater than 6 x 10 to the 20th/cu cm. This is consistent with a 'flux limit' smaller than 0.1. The estimated values of Te and Ne are lower in the corona plasmas produced using the fundamental (1.06 micron) irradiation.

Goldsmith, S.↗
NASA NTRS1985

Short wavelength laser calculations for electron pumping in Be I and B I isoelectronic sequences (Z greater than or equal to 18 and less than or equal to 36)

There has been considerable interest in creating large laser gains in the X-ray region from atomic transitions in ne-like ions formed in high-temperature plasmas. Although the Ne-like ions habe received the most attention, it is also possible to produce population inversions in ions of other isoelectronic sequences. Accordingly, it is shown that certain levels of the 2s3p and 2s(2)3p configurations in the Be I and B I isoelectronic sequences can be inverted by collisional pumping relative to levels of the 2s3s and 2s(2)3s configurations. Level populations and gain coefficients were calculated for the most promising transitions, and opacities were calculated for 2s2p-2s3s and 2s(2)2p-2s(2)3s transitions.

Feldman, U.↗
NASA NTRS1985

Transitions of the type 2s-2p in fluorinelike and oxygenlike As, Se, Br, and Rb

Transitions of the type 2s-2p in the F I and O I isoelectronic sequences of arsenic, selenium, bromine, and rubidium have been identified in spectra from laser-produced plasmas. Wavelengths in the range 50 to 90 A were measured to an accuracy of 0.01 A or better. The wavelengths of the magnetic-dipole transitions within the ground configurations are predicted.

Feldman, U.↗
NASA NTRS1985

Evidence for gain on the C VI 182 A transition in a radiation-cooled selenium/Formvar plasma

Thin plastic foils coated with selenium have been irradiated using from 4 to 8 beams of the OMEGA laser in a line focus configuration. Spectra were recorded using a 3 meter spectrograph that viewed the plasma along the line focus. Based on a comparison of the intensities of the spectral lines from plasmas with lengths of 1.7, 3.4, 6.8, and 13.6 mm, the C VI n = 3 to 2 transition at 182 A was anomalously intense in the spectra from the longer plasmas. Calculations indicate that the carbon plasma was cooled by radiation from the highly-charged selenium plasma in a time that was smaller than the expansion time of the plasma. These plasma conditions are favorable for the occurrence of population inversions between the n = 2 and 3 levels of C VI resulting from recombination and cascading from higher levels. The measured gain coefficient for the C VI 182 A transition is 3/cm, and this corresponds to a gain-length product of 4 in the longest plasma.

Seely, J. F.↗
NASA NTRS1985

Transitions of the type 2s-2p in highly ionized Cu, Zn, Ga, and Ge

Transitions of the type 2s-2p in the F I, O I, N I, and C I isoelectronic sequences of copper, zinc, gallium, and germanium have been identified in the spectra from plasmas produced by the Omega laser system at the University of Rochester. The wavelengths are in the range 50 to 112 A and are measured using silicon and oxygen lines as wavelength standards for gallium and using several lines from the F I, O I, and Na I isoelectronic sequences as wavelength standards for copper, zinc, and germanium. The energy levels that are determined from the measured wavelengths are also presented. Based on these measurements, the wavelengths for a number of magnetic-dipole transitions within the ground configurations of the F I, O I, and N I isoelectronic sequences are predicted.

Behring, W. E.↗
NASA NTRS1985

High-resolution X-ray spectra of solar flares. VII - A long-duration X-ray flare associated with a coronal mass ejection

It has been recognized that very long duration X-ray events (lasting several hours) are frequently associated with coronal mass ejection. Thus, Sheeley et al. (1983) found that the probability of the occurrence of a coronal mass ejection (CME) increases monotonically with the X-ray event duration time. It is pointed out that the association of long-duration, or long-decay, X-ray events (LDEs) with CMEs was first recognized from analysis of solar images obtained by the X-ray telescopes on Skylab and the Naval Research Laboratory (NRL) slitless spectroheliograph. Recently high-resolution Bragg crystal X-ray spectrometers have been flown on three spacecraft, including the Department of Defense P78-1 spacecraft, the NASA Solar Maximum Mission (SMM), and the Japanese Hinotori spacecraft. In the present paper, P78-1 X-ray spectra of an LDE which had its origin behind the solar west limb on November 14, 1980 is presented. The obtained data make it possible to estimate temperatures of the hottest portion of the magnetic loops in which the emission arises.

Kreplin, R. W.↗
NASA NTRS1985

Population mechanisms for the He(+) n = 3 levels determined from measurements of the solar 1640 A emission

The 1640 A line profile is analyzed using solar data obtained by the NRL slit spectrograph on Skylab. Data from coronal hole regions, quiet sun regions, active regions, prominence regions, and flare regions are presented. The relative densities of 3s, 3p, and 3d levels are determined from the data, and the dominant population mechanisms for these levels are inferred using a rate equation model for the He(+) ion. The relative importance of collisional excitation, radiative recombination, and photoexcitation is determined for each of the solar regions.

Seely, J. F.↗
NASA NTRS1985

New identifications of Fe XVII spectral lines in solar flares

The identifications of Fe XVII transitions between the 2s(2)2p(5)3s, 3p, and 3d configurations published by Jupen (1984) are reviewed. The review is based on examining spectroheliograms of solar flares obtained by a Naval Research Laboratory instrument on Skylab (S082-A). Agreement is obtained with the majority of identifications given by Jupen, but different wavelengths are found for a few of the lines. The relative intensities of the lines are qualitatively in agreement with calculations. A broad line at 1153.20 A is identified with the 2p(5)3s(3)P(0)-2p(5)3s(3)P1 forbidden transition of Fe XVII. This line was found in flare spectra obtained by the NRL slit spectrograph on Skylab (S082-B).

Feldman, U.↗
NASA NTRS1984

Scaling of collisionally pumped 3s-3p lasers in the neon isoelectronic sequence

Atomic-number scaling in the 3p-3s population-inversion and plasma parameters of neonlike ions of Si, Ar, Ti, Fe, Ge, and Kr is investigated theoretically. The population levels are calculated; the Z-scaling relationships are defined; the results are presented in tables and graphs; and the implications for the laser gain are explored. Laser gain in excess of 1/cm are predicted for all ions except Si V, with a peak of 30/cm for Fe XVII at electron density 10 to the 21st/cu cm.

Feldman, U.↗
NASA NTRS1984

Direct measurement of the increase in altitude of the soft X-ray emission region during a solar flare

The upward motions of the hot thermal regions of several large (M type) solar flares have been determined from the soft X-ray spectral data recorded by the scanning spectrometer (SOLFLEX) on the P78-1 spacecraft. For the limb flares that are studied, the centroid of the Ca XIX emission region moves to a higher altitude with an apparent speed of 20-40 km/s for a period of 20-30 minutes following onset of the flare and reaches an altitude of 30,000-40,000 km. Although brief periods of downward motion of the emission centroid are observed, substantial decreases in altitude are not observed in any of the flares.

Seely, J. F.↗