Atomic data and spectral line intensities for Si VIII

Bhatia, A. K.; Landi, E.

doi:10.1016/j.adt.2003.08.002

Cited by 10 publications

(13 citation statements)

References 34 publications

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“…However, the potential of these diagnostics is currently limited due to the lack of accurate atomic data. There are inconsistencies between the observed and theoretical predictions for line intensities of N-like Mg VI and Si VIII ions due to the atomic data for these ions (Bhatia & Landi 2003).…”

Section: Introductionmentioning

confidence: 93%

“…In our scattering calculations a total of 1076 CSFs were used to describe the target states of both even parity and odd parity. The calculated excitation energies from the latter calculation are listed in Table 1 together with the calculation of Bhatia & Landi (2003) and experimental energies. The present calculation represents an improvement over the calculation of Bhatia & Landi (2003) who used a set of the same orthogonal one-electron orbitals to represent all target states.…”

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

“…The calculated excitation energies from the latter calculation are listed in Table 1 together with the calculation of Bhatia & Landi (2003) and experimental energies. The present calculation represents an improvement over the calculation of Bhatia & Landi (2003) who used a set of the same orthogonal one-electron orbitals to represent all target states. They calculated energy levels, oscillator strengths and radiative rates by using the Superstructure program of Eissner & Nussbaumer (1974) in intermediate coupling.…”

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

“…We believe that our wave functions correctly represent the main correlation corrections, the interactions between different Rydberg series and term dependence effects. The theoretical lifetimes calculated in length form for various fine-structure levels are also displayed in last column of Table 1. The oscillator strengths and transition probabilities for some dipole transitions E1 from the ground 2s 2 2p 3 4 S o 3/2 and excited metastable 2 D o 3/2 and 2 P o 3/2 levels have been compared with the CI calculations of Bhatia & Landi (2003) and Tachiev & Froese Fischer (2002) in Table 2. The initial and final levels of a transition are given in Cols.…”

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

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Breit-Pauli oscillator strengths and electron excitation collision strengths for Si VIII

Tayal

2012

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Aims. Oscillator strengths and electron impact excitation collision strengths for transitions between the 68 fine-structure levels of the 2s 2 2p 3 , 2s2p 4 , 2p 5 , 2s 2 2p 2 3s, 2s 2 2p 2 3p, 2s 2 2p 2 3d and 2s2p 3 3s configurations in Si VIII are calculated. Thermally averaged collision strengths are presented as a function of electron temperature for application to solar and other astrophysical plasmas. Methods. The collision strengths have been calculated using the B-spline Breit-Pauli R-matrix method for allowed and forbidden transitions in Si VIII. The relativistic effects have been incorporated through mass, Darwin and spin-orbit one-body operators in the Breit-Pauli Hamiltonian in the scattering calculation, while in the calculation of oscillator strengths the one-body and two-body relativistic operators are included. Flexible non-orthogonal sets of spectroscopic and correlation radial functions are used to obtain accurate description of Si VIII levels and to represent the scattering functions. The 68 fine-structure levels of the 2s 2 2p 3 , 2s2p 4 , 2p 5 , 2s 2 2p 2 3s, 2s 2 2p 2 3p, 2s 2 2p 2 3d and 2s2p 3 3s configurations have been considered in both the radiative and scattering calculations. The present scattering calculations are more extensive than previous ones, leading to a total 2278 transitions between fine-structure levels. Results. The calculated excitation energies are in excellent agreement with experiment and represent an improvement over the previous calculations. The present collision strengths show reasonable agreement with the previously available R-matrix and distorted-wave calculations. The oscillator strengths for E1 transitions normally compare very well with previous calculations. The effective collision strengths are obtained by integrating total resonant and non-resonant collision strengths over a Maxwellian distribution of electron energies and these are presented over a wide temperature range from 10 4 to 4.0 × 10 6 K.

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Section: Introductionmentioning

confidence: 93%

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

Section: Excitation Energies Oscillator Strengths and Lifetimesmentioning

confidence: 99%

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Breit-Pauli oscillator strengths and electron excitation collision strengths for Si VIII

Tayal

2012

A&A

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“…The Mg VI line intensity ratios between the n = 2 and n = 3 levels are temperature sensitive and can be used as plasma temperature diagnostics over a wide temperature range of the solar corona. There are inconsistencies between the observed and theoretical predictions for line intensities of N-like Mg VI and Si VIII ions due to the atomic data for these ions (Bhatia & Landi 2003;Young et al 1998). For example, there are discrepancies between theory and observations from the SERTS for the Mg VI 2s 2 2p 3 2 D • -2s2p 4 2 P, 2 D and 2s 2 2p 3 4 S • -2s2p 4 4 P lines which have been attributed to the inaccuracies in the atomic data .…”

Section: Introductionmentioning

confidence: 99%

Oscillator strengths and effective collision strengths for electron excitation of Mg VI

Tayal

2012

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Aims. Electron impact excitation collision strengths and oscillator strengths for the astrophysically important lines in Mg VI are reported. Thermally averaged collision strengths are presented as a function of electron temperature for application to solar and other astrophysical plasmas. Methods. The collision strengths were calculated in a close-coupling approximation using the B-spline Breit-Pauli R-matrix method. The multiconfiguration Hartree-Fock method with term-dependent, non-orthogonal orbitals was employed for an accurate representation of the target wave functions. The close-coupling expansion includes 74 bound levels of Mg VI covering the n = 2 and n = 3 terms. The present calculations led to a total of 2701 forbidden, intercombination, and allowed transitions between fine-structure levels. The effective collision strengths were obtained by averaging the electron collision strengths over a Maxwellian distribution of velocities.Results. The accuracy of present oscillator strengths is evaluated by the agreement between the length and velocity formulations combined with the agreement between the calculated and measured excitation energies. The calculated excitation energies are in excellent agreement with experiments and other extensive configuration-interaction calculations. The oscillator strengths for all E1 transitions are listed. The effective collision strengths are tabulated for all 2701 transitions among the 74 fine-structure levels at 11 electron temperatures in the range from 10 000 to 200 000 K. The present results are compared with other close-coupling and distorted-wave calculations. Overall good agrement is generally found with the calculations by Ramsbottom & Bell and by Landi & Bhatia for many transitions, but significant differences are also noted for some transitions.

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