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  • 1
    Electronic Resource
    Electronic Resource
    3s–3p laser gain and x-ray line ratios for the carbon isoelectronic sequence (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 3953-3957 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The populations of the 46 levels belonging to the configurations 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, and 2s22p3d have been calculated for ions in the C I isoelectronic sequence with atomic numbers Z=18, 22, 26, 30, 34, and 36 and for electron densities from 1015 to 1022 cm−3. The populations of the 2s22p3p levels are relatively large owing to the large electron collisional monopole excitation rates from the ground configuration and to the small radiative decay rates to the ground configuration. This results in population inversions for transitions of the type 3s–3p. The gain coefficients for these transitions are determined and are compared to previous calculations. At high electron densities where collisional mixing of the excited levels becomes important, the intensities of the x-ray transitions from the 2s22p3p levels to the 2s2p3 levels decrease relative to the x-ray transitions from the 2s22p3s and 2s22p3d levels. The density dependence of these x-ray line ratios is also presented. These line ratios represent a promising diagnostic for electron density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336695
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  • 2
    Electronic Resource
    Electronic Resource
    Density sensitive x-ray line ratios in the Be i, B i, and Ne i isoelectronic sequences (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3954-3958 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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 2sn 2pm 3p configuration, relative to the intensities from the 2sn 2pm 3s and 2sn pm 3d configurations, are strong functions of electron density in high-density plasmas. The density sensitivity occurs at electron densities between 1016 cm−3 (for Si ions) and 1022 cm−3 (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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335569
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of resonance excitation due to dielectronic capture on the gain coefficients of selected transitions in Fe XVII (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 3984-3986 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In previous papers, U. Feldman, J. F. Seely, and A. K. Bhatia [J. Appl. Phys. 56, 2475 (1984)] and A. K. Bhatia, U. Feldman, and J. F. Seely [At. Data Nucl. Data Tables (in press)] have calculated atomic data and gain coefficients for ions of the Ne I isoelectronic sequence. Their calculations of electron impact excitation rates were carried out in the distorted wave approximation. They did not include the effect of resonance excitation, i.e., dielectronic capture by a Ne-like ion followed by autoionization leaving the Ne-like ion in an excited state. In this paper, we use the recent calculations of this process by B. W. Smith, J. C. Raymond, J. B. Mann, and R. D. Cowan [Astrophys. J. (in press)] to explore the effect of resonance excitation on gain coefficient calculations for the ion Fe XVII. We find substantial differences (factors of about 1.3–3) between gain coefficient calculations with and without the inclusion of resonances at low temperatures. However, these effects are not important at the temperatures considered by Feldman, Seely, and Bhatia for Fe XVII.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335573
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  • 4
    Electronic Resource
    Electronic Resource
    Electron temperature and average density in spherical laser-produced plasmas: Ultraviolet plasma spectroscopy (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4011-4014 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: 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 μm) and the frequency-tripled (351 nm) output of the Omega laser system. Spectra were recorded in the wavelength region 15–200 A(ring). 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±600 eV and Ne〉6×1020 cm−3. 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 μm) irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336288
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  • 5
    Electronic Resource
    Electronic Resource
    Laser gain on 3p-3d and 3s-3p transitions and x-ray line ratios for the nitrogen isoelectronic sequence (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2248-2252 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The populations of the 72 levels belonging to the 2s22p3, 2s2p4, 2p5, 2s22p23s, 2s22p23p, and 2s22p23d configurations of the N i isoelectronic sequence have been calculated for the ions Ar xii, Ti xvi, Fe xx, Zn xxiv, and Kr xxx and for electron densities up to 1024 cm−3. Electron collisional monopole excitation from the 2s22p3 ground configuration to the 2s22p23p configuration contributes significantly to the populations of the excited levels and results in relatively large 2s22p23p populations. The population inversions and laser gain for transitions between the 2s22p23s and 2s22p23p configurations are calculated. It is also found that large population inversions and gain occur between levels in the 2s22p23p configuration and levels in the 2s22p23d configuration that cannot decay to the ground configuration by an electric dipole transition. For these potential laser transitions of the type 2s22p23p-2s22p23d, the reabsorption of the radiation from the lower laser level is less of a problem than for the 2s22p23s-2s22p23p laser transitions. The 2s22p23p 4P5/2-2s22p23d 4D7/2 and 2s22p23p 2F7/2-2s22p23d 2G9/2 transitions represent promising transitions for overcoming some of the problems of opacity in dense plasmas. At high electron densities where the excited levels become collisionally mixed, the intensities of the x-ray transitions from the 2s22p23p levels to the 2s2p4 levels decrease relative to the x-ray transitions from the 2s22p23s and 2s22p23d levels. The density dependence of these x-ray line ratios is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344279
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  • 6
    Electronic Resource
    Electronic Resource
    Novel target configurations for selective ionization state studies in molybdenum (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5422-5427 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Details of experiments aimed at achieving low ionization state selectivity in molybdenum are presented. Targets are excited with a 10 J CO2 laser and the resultant vacuum ultraviolet spectrum (300–700 A(ring)) has been studied. Combinations of focal spot size, target depth, and target geometries are compared. Simple attenuation of energy is shown not to vary ionization stage composition significantly. Experiments conducted with grazing incidence targets result only in a hot plasma. Modular targets with cooling cylinders of various radii demonstrated good selectivity of the ionization states, but with low absolute signals. Finally, results from combinations of focal spot adjustment and radiative cooling illustrate increased control over desired plasma temperature and density for spectroscopic studies of molybdenum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347192
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  • 7
    Electronic Resource
    Electronic Resource
    Density sensitive line ratios for highly ionized atoms of the Cu i and Na i isoelectronic sequences (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 3947-3952 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We discuss extreme ultraviolet and x-ray spectral lines emitted by ions of the Cu i and Na i isoelectronic sequences and show that certain intensity ratios of these lines are sensitive to electron density in the range from about 1018 to 1022 cm−3. These lines therefore provide density diagnostics for high-temperature plasmas. We illustrate the density dependence for four ions of the Cu i sequence (Z=60, 71, 82, 92) and seven ions of the Na i sequence (Z=32, 42, 52, 62, 72, 82, 92). We also show that the dependence of the ratios on electron temperature is not strong, and demonstrate that opacity can be kept small by employing the spot spectroscopy technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346280
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  • 8
    Electronic Resource
    Electronic Resource
    X-ray imaging of targets irradiated by the Nike KrF laser : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1099-1102 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Foil targets irradiated by the Naval Research Laboratory Nike KrF laser were imaged in the x-ray region with two-dimensional spatial resolution in the 2–10 μm range. The images revealed the smoothness of the emission from target and backlighter foils, the acceleration of the target foils, and the growth of Rayleigh–Taylor instabilities that were seeded by patterns on the irradiated sides of CH foils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147796
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  • 9
    Electronic Resource
    Electronic Resource
    High-resolution x-ray imaging of planar foils irradiated by the Nike KrF laser (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1397-1401 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thin plastic (CH) foils were irradiated by the Naval Research Laboratory Nike [Obenschain et al., Phys. Plasmas 3, 2098 (1996)] KrF laser and were imaged in the x-ray and extreme ultraviolet regions with two-dimensional spatial resolution in the 3–10 μm range. The CH foils were backlit by a silicon plasma. A spherically curved quartz crystal produced monochromatic images of the Si+12 resonance line radiation with energy 1865 eV that was transmitted by the CH foils. Instabilities that were seeded by linear ripple patterns on the irradiated sides of CH foils were observed. The ripple patterns had periods in the 31–125 μm range and amplitudes in the 0.25–5.0 μm range. The silicon backlighter emission was recorded by an x-ray spectrometer, and the 1865 eV resonance line emission was recorded by a fast x-ray diode. The multilayer mirror telescope recorded images of the C+3 1550 Å emission (energy 8.0 eV) from the backside of the CH foils. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872315
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  • 10
    Electronic Resource
    Electronic Resource
    A review of the first ionization potential effect on elemental abundances in the solar corona and in flares (2002)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 629-635 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The elemental composition of solar upper atmosphere plasmas was studied from spectra obtained by instruments aboard all major solar observatories that were launched into space in the last three decades. The studies show that the first ionization potential (FIP) of the elements has a profound effect on their abundance in the various solar upper atmosphere regions. In this paper we review properties of the FIP effect as they relate to coronal holes, quiet regions, active regions and flares and we show that although the derived compositions vary considerably with the type of plasma observed regularities in their behavior are emerging. The observed behavior may help identify the energy deposition mechanism that fuels the corona and solar flares. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1435000
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