Impact excitation of the<i>n=2</i>fine-structure levels in hydrogenlike ions by protons and electrons

Zygelman, B.; Dalgarno, A.

doi:10.1103/physreva.35.4085

Cited by 37 publications

(21 citation statements)

References 18 publications

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“…Our results of Ω for "elastic" transitions may be underestimated by (over) a factor of two, as can be seen by a comparison with the earlier results of Zygelman & Dalgarno (1987) for the 2−3 and 2−4 transitions. Since the top-up according to the sum rules of Burgess & Tully (1992) results in the overestimation of the contribution of higher neglected partial waves for a majority of allowed (and intercombination) transitions, such as 3−7 transition for which Ω has converged within the partial waves range of the calculations as shown in Fig.…”

Section: Collision Strengthsmentioning

confidence: 50%

Electron impact excitation of Al XIII: A relativistic approach

Aggarwal

Keenan

Rose

2005

A&A

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Abstract.Energy levels, radiative rates, collision strengths, and effective collision strengths for all transitions up to and including the n = 5 levels of Al XIII have been computed in the j j coupling scheme including relativistic effects. All partial waves with angular momentum J ≤ 60 have been included, and resonances have been resolved in a fine energy grid in the threshold region. Collision strengths are tabulated at energies above thresholds in the range 170.0 ≤ E ≤ 300.0 Ryd, and results for effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are tabulated over a wide temperature range of 4.4 ≤ log T e ≤ 6.8 K. The importance of including relativistic effects in a calculation is discussed in comparison with the earlier available non-relativistic results.

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Section: Collision Strengthsmentioning

confidence: 50%

Electron impact excitation of Al XIII: A relativistic approach

Aggarwal

Keenan

Rose

2005

A&A

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“…We scaled their rates for n = 4 by the absorption oscillator strength to get impact excitation rates going up to np states, and by 1/n 3 for ns and nd states. Proton excitation rates among the n = 2 levels are taken from Zygelman & Dalgarno (1987), and these results are scaled for proton rates among n = 3 and higher levels. Radiative decay rates for E1 transitions were calculated from the expression in terms of hypergeometric functions given in Bethe & Salpeter (1957), and those for the 2E1 transition are taken from Drake & Goldman (1981).…”

Section: Atomic Physics Issuesmentioning

confidence: 99%

The Solar Helium Abundance in the Outer Corona Determined from Observations with SUMER/SOHO

Laming

Feldman

2001

ApJ

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At altitudes of about 1.05 solar radii or more, the corona above quiet solar regions becomes essentially isothermal. This obviates many of the difficulties associated with the inverse problem of determining emission measure distributions, and allows for fairly straightforward relative element abundance measurements. We present new values for the He abundance. The first is based on a reanalysis of the He/O ratio studied previously using data acquired by SUMER. A more thorough evaluation of the atomic physics for He II, including a detailed treatment of radiative recombination, increases the predicted emission in the He II Balmer series compared to earlier analyses. We use a recently revised value of the O abundance to derive an He/H abundance ratio of 0.038, (mass fraction, Y = 0.13), with an error of ∼ 17% coming mainly from the O abundance uncertainty. We demonstrate that this result may be affected by gravitational settling of O relative to He. We also derive an abundance for He by direct comparison to emission lines of the H I Lyman series, with the result He/H = 0.052 ± 0.005 (Y = 0.17), a value similar to He abundances determined in the slow speed solar wind.

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“…We have also assumed that only excitations from the ground state of He + are important. Proton collisions effectively transfer population in the metastable 2s level to the 2p (Zygelman & Dalgarno 1987), and for the optical depths likely in the He II 1s − 2p transition, insufficient population will be present in the 2p levels to affect the populations of higher lying levels (Laming & Feldman 1992). We have neglected proton collisions among the various levels corresponding to n = 7, and have calculated the branching ratio for the Balmer transition in the cases of the optically thick and thin Lyman transition from formulae for + is optically thin or thick.…”

Section: Spectroscopic Diagnostics With Sumermentioning

confidence: 99%

The solar disk spectrum between 660 and 1175 Å (first order) obtained by SUMER on SOHO

Curdt

Feldman

Laming

et al. 1997

Astron. Astrophys. Suppl. Ser.

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Abstract. SUMER -Solar Ultraviolet Measurements of Emitted Radiation -onboard of SOHO -Solar and Heliospheric Observatory -obtained its first spectrum on January 25, 1996 near the north polar limb. The range from 660Å to 1175Å which has never before been observed with such a good spectral resolution contains a wealth of spectroscopic details. Identification of about 400 lines in this spectral range is given. We list the wavelengths of identified transitions and provide their absolute peak intensities. General spectral features of the most abundant elements H, He, C, N, O, Ne, Mg, Si, S, Ar, and Fe are described. In this spectral range many density-and temperature-sensitive line pairs are found. It is shown in examples how they can be used as diagnostic tools.

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Impact excitation of then=2fine-structure levels in hydrogenlike ions by protons and electrons

Cited by 37 publications

References 18 publications

Electron impact excitation of Al XIII: A relativistic approach

Electron impact excitation of Al XIII: A relativistic approach

The Solar Helium Abundance in the Outer Corona Determined from Observations with SUMER/SOHO

The solar disk spectrum between 660 and 1175 Å (first order) obtained by SUMER on SOHO

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