Effective collision strengths for transitions in Fe XIII

Effective collision strengths for transitions among the lowest 97 fine-structure levels belonging to the (1s(2)2s(2)2p(6)) 3s(2)3p(2), 3s3p(3), 3s(2)3p3d, 3p(4), 3s3p(2)3d and 3s(2)3d(2) configurations of Fe XIII have been calculated using the fully relativistic Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2004). Resonances have been resolved in the threshold region, and results are reported over a wide electron temperature range up to log T-e = 6.8 K. Comparisons are made with the earlier available R-matrix results of Gupta & Tayal (1998), and the accuracy of the data is assessed.

Effective collision strengths for transitions in Fe X

Collision strengths for 4005 transitions among the lowest 90 levels of the (1s(2)2s(2)2p(6)) 3s(2)3p(5), 3s3p(6), 3s(2)3p(4)3d, 3s3p(5)3d and 3s(2)3p(3)3d(2) configurations of Fe X have been calculated using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant, over a wide energy range up to 210 Ryd. Resonances have been resolved in the threshold region, and effective collision strengths have been obtained over a wide temperature range up to 107 K. The present calculations should represent a significant improvement ( in both range and accuracy) over the earlier available results of Bhatia & Doschek and Pelan & Berrington. Based on several comparisons, the accuracy of our data is assessed to be better than 20%, for a majority of transitions.

Radiative rates, collision strengths and effective collision strengths for transitions in Mo XXXIV

Radiative rates for electric dipole (E I), electric quadrupole (E2), magnetic dipole (M1), and magnetic quadrupole (M2) transitions among the lowest 60 fine-structure levels of the (1s(2)) 2S(2)2p(5), 2s2p(6), and 2S(2)2p(4)3l configurations of F-like Mo XXXIV have been calculated using the fully relativistic GRASP code. Additionally, collision strengths for transitions among these levels have been computed over a wide energy range below 3200Ry, using the Dirac Atomic R-matrix Code. Resonances have been resolved in a fine energy mesh in order to calculate the effective collision strengths. Results for radiative rates and excitation rates are presented for all transitions, and for collision strengths for transitions from the lowest three levels to the higher lying levels. The accuracy of the present data is assessed to be similar to 20%.

Effective collision strengths for transitions in Fe XI

Collision strengths for transitions among the lowest 48 fine- structure levels belonging to the (1s(2)2s(2)2p(6)) 3s(2)3p(4), 3s3p(5), 3s(2)3p(3)3d and 3p(6) configurations of Fe XI have been calculated using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003). Results are tabulated at energies above thresholds in the range 10 less than or equal to E less than or equal to 100 Ry, although resonances have been resolved in a fine energy mesh in the thresholds region. Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron velocities, are also tabulated over a wide electron temperature range below 5 x 10(6) K. Comparisons with other available results are made, and the accuracy of the present data is assessed.

Effective collision strengths for transitions within the ground configuration of Fe XXI

Effective collision strengths for transitions among the energetically lowest 46 fine-structure levels belonging to the (1s(2)) 2S(2) 2p(2), 2s2p(3), 2p(4), 2S(2)2p3s, 2s(2)2p3p and 2S(2)2p3d configurations of Fe XXI are computed, over an electron temperature range of 5.6 less than or equal to log T-e less than or equal to 7.4 K, using the recent Dirac Atomic R- matrix Code (DARC) of Norrington and Grant. Results are presented for transitions within the ground configuration only, and are compared with earlier R matrix calculations. Large discrepancies are observed for many transitions, especially at lower temperatures.

Radiative rates, collision strengths and effective collision strengths for transitions in Gd XXXVII

Energy levels and radiative rates for transitions among 107 fine-structure levels belonging to the (1s(2)2S(2)p(6)) 3S(2)3p(6)3d(10), 3S(2)3p(6)3d(9)4e. 3S(2)3p(5)3d(10)4e. and 3s3p(6)3d(10)4e configurations of Ni-like Gd XXXVII have been calculated using the fully relativistic GRASP code. Radiative rates and oscillator strengths are tabulated for all allowed transitions among these levels. Additionally. collision strengths for transitions among the lowest 59 levels have been computed using the Dirac Atomic R-matrix Code. Resonances in the threshold region have been delineated, but results for collision strengths are tabulated only at energies above thresholds in the range 120

Effective collision strengths for transitions in Fe XV

Collision strengths for transitions among the energetically lowest 53 fine-structure levels belonging to the (1s(2)2s(2)2p(6)) 3l(2), 3l3l', 3s4l and 3p4s configurations of Fe XV are computed, over an electron energy range below 160 Ryd, using the Dirac Atomic R-matrix Code (DARC) of Norrington & Grant (2003). Effective collision strengths, obtained after integrating the collision strengths over a Maxwellian distribution of electron energies, have also been calculated. These results of effective collision strengths are tabulated for all 1378 inelastic transitions over a wide temperature range of 10(5) to 10(7) K. Comparisons are also made with other R-matrix calculations and the accuracy of the results is assessed.

Effective collision strengths for transitions among the 3s(2), 3s3p and 3p(2) configurations of Fe xv

Effective collision strengths for transitions among the ten energetically lowest fine-structure levels belonging to the (1s(2)2s(2)2p(6))3s(2), 3s3p and 3p(2) configurations of Fe xv have been calculated in the electron temperature range of 10(5)-10(7) K, using the recent Dirac atomic R-matrix code of Norrington and Grant. The results are compared with the other recently available independent Breit-Pauli R-matrix calculations of Eissner et al (Eissner W, Galavis M E, Mendoza C and Zeippen C J 1999 Astron. Astrophys. Suppl. 137 165) and Griffin et al (Griffin DC, Badnell N R, Pindzola M S and Shaw J A 1999 J. Phys. B: At. Mol. Opt. Phys. 32 2139, 4129). Large differences are observed for many transitions over almost the entire temperature range. These differences are analysed and discussed, and the accuracy of the calculations is assessed.

Effective collision strengths for electron impact excitation of C1III

Effective collision strengths for electron-impact excitation of the phosphorus-like ion Cl III are presented for all fine- structure transitions among the levels arising from the lowest 23 LS states. The collisional cross sections are computed in the multichannel close-coupling R-matrix approximation, where sophisticated configuration-interaction wave functions are used to represent the target states. The 23 LS states are formed from the basis configurations 3s(2)3p(3). 3s3p(4). 3s(2)3p(2)3d, and 3s(2)3p(2)4s, and correspond to 49 fine- structure levels, leading to a total possible 1176 fine- structure transitions. The effective collision strengths. obtained by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. are tabulated in this paper for all 1176 transitions and for electron temperatures in the ranges T(K) = 7500-25.000 and log T(K) = 4.4-5.3. The former range encompasses the temperatures of particular importance for application to gaseous nebulae. while the latter range is more applicable to the study of solar and laboratory-type plasmas. (C) 2001 Academic Press.

Effective collision strengths for electron impact excitation of Si VIII

Effective collision strengths for electron-impact excitation of the nitrogen-like ion Si VIII are presented over the wide range of electron temperatures log T(K) = 4.0-6.5. All 231 fine- structure transitions among the 22 fine-structure levels arising from the lowest 11 LS target states (2s(2)2p(3), 2s2p(4), 2p(5), and 2s(2)2p(2)3s) are considered in the tabulation. The collision strengths are evaluated in a multi- channel R-matrix approach, and the corresponding effective collision strengths are obtained by averaging these over a Maxwellian distribution of electron velocities. Comparisons are made with recent distorted-wave results at high incident electron energies. Differences of up to 20% are found, particularly for some allowed transitions. (C) 2003 Elsevier Inc. All rights reserved.

Geometry- and diffraction-independent ionization probabilities in intense laser fields: Probing atomic ionization mechanisms with effective intensity matching

We report an experimental technique for the comparison of ionization processes in ultrafast laser pulses irrespective of pulse ellipticity. Multiple ionization of xenon by 50 fs 790 nm, linearly and circularly polarized laser pulses is observed over the intensity range 10 TW/cm(2) to 10 PW/cm(2) using effective intensity matching (EIM), which is coupled with intensity selective scanning (ISS) to recover the geometry-independent probability of ionization. Such measurements, made possible by quantifying diffraction effects in the laser focus, are compared directly to theoretical predictions of multiphoton, tunnel and field ionization, and a remarkable agreement demonstrated. EIM-ISS allows the straightforward quantification of the probability of recollision ionization in a linearly polarized laser pulse. Furthermore, the probability of ionization is discussed in terms of the Keldysh adiabaticity parameter gamma, and the influence of the precursor ionic states present in recollision ionization is observed.

Effective collision strengths for allowed transitions among the n

Aims.In this paper we report on calculations of collision strengths and effective collision strengths for allowed transitions among the $n \le$ 5 degenerate levels of Al XIII.
Methods.The Dirac atomic R-matrix code (DARC) has been adopted for these calculations.
Results.Collision strengths are reported over a wide energy range below 300 Ryd, and effective collision strengths are provided for electron temperatures of 4.4 $\le$ log $T_{\rm e} \le$ 6.8 K.

Effective collision strengths for transitions in Ni XIX

Aims. In this paper we report electron impact collision strengths and excitation rates for transitions among the lowest 89 levels of Ni XIX.
Methods. The Dirac atomic R-matrix code (DARC) is adopted for the calculations of collision strengths and subsequently the effective collision strengths.
Results. Collision strengths for resonance transitions among 89 levels arising from the (1s2) 2s22p6, 2s22p53$\ell$, 2s2p63$\ell$, 2s22p54$\ell$, and 2s2p64$\ell$ configurations of Ni XIX are reported over a wide energy range below 250 Ryd. Additionally, effective collision strengths for all 3916 transitions among the 89 levels are listed over a wide temperature range below 107 K. Comparisons are made among different calculations and the accuracy of the data is assessed. Finally, comparisons between theoretical and experimental intensity ratios of some prominent lines of Ni XIX are discussed.

Effective collision strengths for inner shell transitions of Fe XVI

Collision strengths for transitions among the energetically lowest 134 levels of the (1s(2)2s(2)) 2p(6)3l, 2p(5)3s(2), 2p(5)3s3p, 2p(5)3s3d, 2p(5)3p3d and 2p(5)3d(2) configurations of Fe XVI are computed, over an electron energy range below 570 Ryd, using the Dirac atomic R-matrix code (DARC) and the flexible atomic code (FAC). All partial waves with J

Breit-Pauli R-matrix calculation of fine-structure effective collision strengths for the electron impact excitation of Mg V

Context. Electron-impact excitation collision strengths are required for the analysis and interpretation of stellar observations.
Aims. This calculation aims to provide effective collision strengths for the Mg V ion for a larger number of transitions and for a greater temperature range than previously available, using collision strength data that include contributions from resonances.
Methods. A 19-state Breit-Pauli R-matrix calculation was performed. The target states are represented by configuration interaction wavefunctions and consist of the 19 lowest LS states, having configurations 2s22p4, 2s2p5, 2p6, 2s22p33s, and 2s22p33p. These target states give rise to 37 fine-structure levels and 666 possible transitions. The effective collision strengths were calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities.
Results. The non-zero effective collision strengths for transitions between the fine-structure levels are given for electron temperatures in the range = 3.0 - 7.0. Data for transitions among the 5 fine-structure levels arising from the 2s22p4 ground state configurations, seen in the UV range, are discussed in the paper, along with transitions in the EUV range – transitions from the ground state 3P levels to 2s2p5?3P levels. The 2s22p4?1D–2s2p5?1P transition is also noted. Data for the remaining transitions are available at the CDS.