Anand K. Bhatia

Atomic data and spectral line intensities for Ne-like Fe XVII

Electron impact collision strengths and spontaneous radiative decay rates are calculated for the Ne-like ion Fe XVII. The data pertain to the 37 levels of the configurations 2s[sup 2]2p[sup 6], 2s[sup 2]2p[sup 5]3s, 2s[sup 2]2p[sup 5]3p, 2s[sup 2]2p[sup 5]3d, 2s2[sup 6]3s, 2s2p[sup 6]3p, and 2s2p[sup 6]3d. Collision strengths are calculated at five energies. In Rydberg units these energies are 76.83, 91.53, 120.93, 179.73, and 253.23. Spectral line intensities are calculated for all transitions with intensities within two orders of magnitude of the most intense line in each ion. These are obtained by computing the excitation rate coefficients (cm[sup 3] s[sup [minus]1]), that is, the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 37 energy levels, assuming a collisional excitation model. The level populations are computed for several electron densities and are also given in this paper. 17 refs., 4 tabs.

Atomic data and spectral line intensities for Fe XI

Electron impact collision strengths and spontaneous radiative decay rates are calculated for Fe XI. The data pertain to the 48 levels of the configurations 3s23p4, 3s3p5, 3s23p33d, and 3p6. Collision strengths are calculated at three incident electron energies, 8.0, 16.0, and 24.0 Ry. Relative spectral line intensities are calculated for all astrophysically important transitions. These are obtained by computing the excitation rate coefficients, i.e., the collision strengths integrated over a Maxwellian electron distribution, and then solving the equations of detailed balance for the populations of the 48 energy levels, assuming a collisional excitation model and an electron temperature of 1.3 × 106K. This temperature is typical for Fe XI when formed in equilibrium by collisional ionization and recombination. Using the excitation rate coefficients and the radiative decay rates, level populations are computed for several electron densities and are given in this paper. We also investigate the effects of proton excitation and solar radiative excitation on the level populations and line intensities. Finally, the calculated relative line intensities are compared with experimental solar intensities where available.

3s--3p laser gain and x-ray line ratios for the carbon isoelectronic sequence

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 ratio...

Spectral line intensities for the O I, N I, C I, B I, and Be I isoelectronic sequences, Z = 26–36☆

Abstract The spectral line intensities for the O I, N I, C I, B I, and Be I isoelectronic sequences and for Z = 26, 28, 30, 32, 34, and 36 are presented. The transitions are of the types 2 s 2 2 p k −2 s 2 p k +1 , 2 s 2 p k +1 −2 p k +2 , 2 s 2 2 p k −2 s 2 2 p k , and 2 s 2 p k +1 −2 s 2 p k +1 . The simulated spectra are useful for the identification of allowed and forbidden transitions in the wavelength range 40 to 2300 A in tokamak plasmas. The line intensities are calculated for an electron density of 2.5 × 10 13 cm −3 and for an electron temperature approximately equal to the temperature for maximum abundance of each ion in the case of coronal equilibrium.

Atomic data and spectral line intensities for Ne III

Abstract Electron impact collision strengths, energy levels, oscillator strengths and spontaneous radiative decay rates are calculated for Ne III. The configurations used are 2s22p4, 2s2p5, 2s22p33s, and 2s22p33d giving rise to 57 fine-structure levels in intermediate coupling. Collision strengths are calculated at five incident energies, 5, 15, 25, 35, and 45 Ry. Excitation rate coefficients are calculated by assuming a Maxwellian electron velocity distribution at an electron temperature of logTe(K)=5.0, corresponding to maximum abundance of Ne III. Using the excitation rate coefficients and the radiative transition rates, statistical equilibrium equations for level populations are solved at electron densities covering the range of 10 8 –10 14 cm −3 . Relative spectral line intensities are calculated. Proton excitation rates between the lowest three levels have been included in the statistical equilibrium equations. The predicted Ne III line intensities are compared with SERTS rocket measurements of a solar active region and of a laboratory EUV light source.

Laser gain on 3p‐3d and 3s‐3p transitions and x‐ray line ratios for the nitrogen isoelectronic sequence

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 2...

EUV Line Intensities of Fe X

The 4 configuration, distorted wave calculation of Bhatia & Doschek (1995) (hereafter referred to as BD95), together with the ground transition calculation of Pelan & Berrington (1995) are here used to predict the intensities of the Fe X EUV lines, which are then used to derive electron densities from several solar spectra, including the recent SERTS spectra.