A. Tauheed

Beam-foil lifetime study of Al-like titanium, iron and nickel

The lifetimes of the resonance levels in the Al-like ions Ti X, Fe XIV and Ni XVI have been obtained from beam-foil measurements using a variety of analytical techniques. The spectral analysis and identification of cascade transitions necessary for application of the ANDC procedure have been aided by recent observations of laser-produced plasmas. The lifetime values obtained from ANDC analyses for the 3s 3p2 doublet levels agree well with predictions based on semi-empirical Hartree-Fock calculations. However, the ANDC results for the 3s2 3d levels fall between the values obtained using multi-exponential curve-fitting and from the calculations.

The 5s25p 2P-5s5p2 4P intercombination lines in the In I isoelectronic sequence from Sb III to La IX

The 5s25p 2P-5s5p2 4P intercombination lines in indium-like ions have been identified from Sb III to La IX. For Sb III and Te IV previously reported values are confirmed and for I V, the 5s5p2 4P32 level have been revised while all other 5s5p2 4P levels for all spectra have been reported for the first time. Thirty-three lines are classified, of which 20 are new.

Extended and revised analysis of singly ionized tin: Sn II

The electronic structure of singly ionized tin (Sn II) is partly a one-electron and partly a three-electron system with ground configuration 5s25p. The excited configurations are of the type 5s2nl in the one-electron part, and 5s5p2, 5p3 and 5s5pnl (nl = 6s, 5d) in the three-electron system with quartet and doublet levels. The spectrum analyzed in this work was recorded on a 3 m normal incidence vacuum spectrograph of the Antigonish laboratory (Canada) in the wavelength region 300 A–2080 A using a triggered spark source. The existing interpretation of the one-electron level system was confirmed in this paper, while the 2S1/2 level of the 5s5p2 configuration has been revised. The analysis has been extended to include new configurations 5p3, 5s5p5d and 5s5p6s with the aid of superposition-of-configurations Hartree–Fock calculations with relativistic corrections. The ionization potential obtained from the ng series was found to be 118 023.7(7) cm−1 (14.633 07(8) eV). We give a complete set of critically evaluated data on energy levels, observed wavelengths and transition probabilities of Sn II in the range 888–10 740 A involving excitation of the n = 5 electrons.

Revised and extended analysis of the 5s25p3, 5s5p4, 5s25p25d and 5s25p26s configurations of trebly ionized xenon (Xe IV)

The spectrum of xenon was photographed in the 350 A-2000 A region on a 3-m normal incidence spectrograph. The source used was a modified triggered spark. Of 31 previously reported levels of the 5s5p4, 5s25p25d and 5s25p26s configurations of Xe IV, two were rejected, J-values of two levels were altered and LS-designations of three levels were revised. Fourteen additional levels have been established. Configuration interaction calculations for the 5s5p4, 5s25p25d, 5s25p26s and 5s25p26d configurations were carried out to interpret the observed spectrum. 114 lines are now classified in this spectrum, of which 34 are new identifications.

Analysis of the four lowest configurations of five times ionized cesium (Cs VI)

The spectrum of cesium was photographed in the 325-1400 A region on 3-m and 10.7-m normal-incidence spectrographs using a triggered-spark source. Sixty-seven lines have been classified as transitions between levels of fivetimes ionized cesium. The analysis has determined all levels of the 5s2 5p2 ground configuration and all but the J = 4 level of the three lowest excited configurations, 5s5p3, 5s25p5d and 5s25p6s. Multiconfiguration calculations were performed and least-squares fitted parameters are given.

Revised and extended analysis of doubly ionized selenium: Se III

The spectrum of selenium was recorded on a 3 m normal incidence vacuum spectrograph of the Antigonish laboratory (Canada) in the wavelength region 300–2080 A using a triggered spark source. The theoretical structure of doubly ionized selenium (Se III) was predicted by Cowans multi-configuration interaction code. The ground configuration of Se III is 4s24p2 and the excited configurations are of the type 4s24pnd (n≥4), 4s24pns (n≥5) and the inner shell excitation gives rise to the 4s4p3 configuration. The 4s24p2−[4s4p3+4s24p (4d+5d+6d+7d+5s+6s+7s+8s)] transition array has been analyzed. Several earlier reported levels have been revised and four new configurations have been added. All the levels of these configurations have been established. More than 180 spectral lines have been identified in this spectrum. A total of 75 energy levels belonging to the above-mentioned configurations have been established. Least-squares fitted parametric and Hartree–Fock calculations were used to interpret the observed spectrum. Excellent agreement with theoretical calculations was noticed. The standard deviation of least-squares fit is only 110 cm−1. The ionization potential of Se III was found to be 255 650±150 cm−1 (31.696±0.018 eV). The accuracy of our wavelengths for sharp lines is better than ±0.005 A.

Analysis of four times ionized cesium (Cs V)

The spectrum of cesium was photographed in the 300-1240 A region on a 3-m normal incidence spectrograph. The source used was a triggered spark. The 5s25p2-(5s5p4 + 5s25p25d + 5s25p26s) transition array of Cs V spectrum was analysed. All levels of the ground state configuration 5s25p3 and all but two levels out of a possible 44 levels of the three even parity excited configurations have been established. One hundred and forty-two lines have been classified in this spectrum. Least squares fitted parametric calculations involving configuration interactions have been carried out to interpret the observed spectrum.

Spectrum and energy levels of triply ionized barium (Ba iv)

The spectrum of Ba iv was observed with sliding sparks and low-inductance vacuum sparks on 10.7- and 3-m normal-incidence vacuum spectrographs. Thirty-nine lines between 463 and 923 A are classified as transitions between levels of the 5s25p5 2P ground term and levels of the 5s5p6, 5s25p45d, and 5s25p46s configurations. These configurations are theoretically interpreted, and the energy parameters determined from least-squares fits to the observed levels are compared with Hartree–Fock calculations. The ionization energy is revised to 379 300 ± 2700 cm−1 (47.03 ± 0.33 eV).

SEVENTH SPECTRUM OF LANTHANUM : LA VII

The spectra of lanthanum ions were photographed in the 90A–1220A region on a 3-m normal incidence spectrograph at the Antigonish laboratory and a 10.7m grazing incidence spectrograph at the NIST laboratory. The source used in both laboratories was a triggered spark. The 5s25p3–(5s5p4+5s25p25d+5s25p26s) transitions of La VII were analysed. All five levels of the ground state and 37 of 44 levels of the 5s5p4+5s25p25d+5s25p26s configurations have been established. 102 lines have been classified in the 307–1005A region. Hartree–Fock (HFR) and Least-Squares-Fit (LSF) calculations were carried out to interpret the spectrum.

Sixth spectrum of lanthanum (La VI): analysis of the , and configurations

The spectrum of lanthanum was photographed in the 300 - 1220 A wavelength region on a 3 m normal incidence and a 10.7 m grazing incidence spectrograph using a triggered spark source. The - transitions of La VI were analysed. We have confirmed the earlier analysis of Reader of the - transitions. Of 52 possible levels of the three odd configurations 42 have been established. Six of the 10 unknown levels have and give no transitions to the ground-state configuration. One hundred and three lines have been classified in the La VI spectrum. The least-squares-fitted and relativistic Hartree - Fock calculations were carried out to interpret the observed spectrum.