Computer programs for the calculation of electron-atom collision cross sections. I. General formulation

Eissner, W.; Seaton, M. J.

doi:10.1088/0022-3700/5/12/013

Cited by 355 publications

(97 citation statements)

References 7 publications

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“…In these programs, which have been updated over the years, the energy levels and radiative data are calculated using the Superstructure Program described by Eissner, Jones, & Nussbaumer (1972). The scattering problem is carried out in the distorted wave approximation using the program described by Eissner & Seaton (1972) and Eissner (1998). The collision strengths are then calculated using the program JAJOM developed by Saraph (1978) and modified by H. E. Saraph & W. Eissner (2001, private communication).…”

Section: Theoretical Methodsmentioning

confidence: 99%

The Effect of High‐lying Levels on Atomic Models Relevant to Spectroscopic Analyses of Solar Extreme‐Ultraviolet Spectra

Doron

Doschek

Feldman

et al. 2002

ApJ

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In this work we investigate the effect of including high-lying configurations in the collisional-radiative models used to calculate spectral line intensities recorded by the Solar Ultraviolet Measurement of Emitted Radiation (SUMER) spectrometer on board the SOHO satellite. Many of the emission lines observed by SUMER are attributed to transitions within the L and M electronic shells of ions isoelectronic to sequences from Li i to Na i. By using atomic data that are mostly generated by the Hebrew University Lawrence Livermore Atomic Code (HULLAC), we incorporate in the atomic models configurations from higher shells and systematically study their effect on the calculated line intensities in selected ions. The high-lying configurations alter the line intensities through radiative cascades and configuration interaction effects. We find that cascades can significantly enhance the line intensities of the considered ions by up to 60% at temperatures of the ion maximum fractional abundance. The enhancement due to cascades increases with increasing temperature and charge state. The configuration mixing effects can either enhance or reduce the line intensities. Generally, the mixing effect becomes less important for higher charge states.

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Section: Theoretical Methodsmentioning

confidence: 99%

The Effect of High‐lying Levels on Atomic Models Relevant to Spectroscopic Analyses of Solar Extreme‐Ultraviolet Spectra

Doron

Doschek

Feldman

et al. 2002

ApJ

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“…Therefore, to make an accuracy assessment for Ω, we have performed another calculation using the fac code of Gu [12]. This code is also fully relativistic, and is based on the well-known and widely-used distorted-wave (DW) method -see for example, [28]- [29] and the FAC manual. Furthermore, the same CI is included in fac as in the calculations from darc.…”

Section: Collision Strengthsmentioning

confidence: 99%

Energy levels, radiative rates and electron impact excitation rates for transitions in He-like Mg XI, Al XII, P XIV and S XV

Aggarwal¹,

Keenan²

2012

Phys. Scr.

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We report calculations of energy levels, radiative rates and electron impact excitation cross sections and rates for transitions in Be-like Ti XIX. The grasp (General-purpose Relativistic Atomic Structure Package) is adopted for calculating energy levels and radiative rates. For determining the collision strengths and subsequently the excitation rates, the Dirac Atomic R-matrix Code (darc) is used. Oscillator strengths, radiative rates and line strengths are reported for all E1, E2, M1 and M2 transitions among the lowest 98 levels of the n ≤ 4 configurations. Additionally, theoretical lifetimes are listed for all 98 levels. Collision strengths are averaged over a Maxwellian velocity distribution and the effective collision strengths obtained listed over a wide temperature range up to 10 7.7 K. Comparisons are made with similar data obtained from the Flexible Atomic Code (fac) to highlight the importance of resonances, included in calculations with darc, in the determination of effective collision strengths. Discrepancies between the collision strengths from darc and fac, particularly for forbidden transitions, are also discussed.2

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“…Under such conditions, the low-density line intensity ratio reads where the excitation rate coefficient q ij is with g i being the statistical weight of the initial level and being the ϒij Maxwellian-averaged collision strength A purely algebraic transformation from the LS coupling to a pair-coupling representation may be employed to obtain finestructure LSJ collision strengths, which should be accurate provided the relativistic effects are negligible. The transformation coefficients are particularly simple when the initial LS term has L or S = 0, and This procedure was employed by P76a,b using the IMPACT close-coupling codes (Eissner and Seaton 1972, 1974, Crees et al 1978. It is then clear that in the low-density limit But the above analysis is predicated on the assumption that LS coupling is valid and there is no deviation due to relativistic effects.…”

Section: Introductionmentioning

confidence: 99%

Relativistic and correlation effects in electron impact excitation of forbidden transitions of OII

Montenegro

Eissner²,

Nahar

et al. 2006

J. Phys. B: At. Mol. Opt. Phys.

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We investigate relativistic and correlation effects in electron impact excitation of singly ionized oxygen using the Breit-Pauli R-matrix method. 1/ 2)shows that the finestructure collision strengths do not significantly depart from the values obtained from a purely LS → LSJ transformation, and relativistic effects are therefore small. We find that the Maxwellian-averaged effective collision strengths for the ten transitions also differ from the previous work, most likely due to more extensive delineation of resonances in the present work. However, the differences are largely systematic and therefore the OII line intensity ratios are not significantly affected. We also obtain an excellent agreement between the present-calculated cross sections for the 4 S o -2 D o transition and the experimental merged beam measurements.

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Computer programs for the calculation of electron-atom collision cross sections. I. General formulation

Cited by 355 publications

References 7 publications

The Effect of High‐lying Levels on Atomic Models Relevant to Spectroscopic Analyses of Solar Extreme‐Ultraviolet Spectra

The Effect of High‐lying Levels on Atomic Models Relevant to Spectroscopic Analyses of Solar Extreme‐Ultraviolet Spectra

Energy levels, radiative rates and electron impact excitation rates for transitions in He-like Mg XI, Al XII, P XIV and S XV

Relativistic and correlation effects in electron impact excitation of forbidden transitions of OII

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