K Rahimullah

The 4p-4d Transitions of Y VI, VII, VIII, Zr VII, VIII, IX, Nb VIII, IX, X and Mo IX, X, XI

On recordings made in the Physics Department of Lund University, we have identified 64, 65, 63 and 71 4p-4d transitions in Y VI, Zr VII, Nb VIII and Mo IX, respectively, establishing 23 levels of 4p34d in each case. In Y VII, Zr VIII, Nb IX and Mo X we have identified 54, 53, 48 and 57 4p-4d transitions, establishing 19 levels of 4p24d in each spectrum. The number of 4p-4d transitions identified in Y VIII, Zr IX, Nb X and Mo XI is 28, 27, 27 and 31; they establish all the 11 4p4d levels that can combine with the ground levels. In addition, two levels of 4s4p3 could be found from 4s-4p transitions.

4p-5s Transitions in Y VII, VIII, Zr VIII, IX, Nb IX, X and Mo X, XI

The spectra of Y VII, VIII, Zr VIII, IX, Nb X and Mo X, XI are studied for the first time and our 1971 analysis of Nb IX is improved. By analyses of the transitions 4s24pk-4s24pk-15s all the levels of the configurations 4p3, 4p25s, 4p2 and 4p5s are established in the spectra concerned.

Classified Lines and Energy Levels of Doubly Ionized Zirconium (Zr III)

Based on Lund recordings, this communication reports 380 classified lines of the doubly ionized zirconium atoms. These classifications led us to confirm the energy levels belonging to the configurations 4s24p64d2, 4d5s, 4d6s, 4d5p, 4d5d, 4d4f, 5s6s, 5s5p, 5s5d, 5s4f and 5p2. All the levels of 4d6p and 5s2 have been revised, along with 1H5 of 4d4f. The configurations 4d6d, 4d5f, 5s6p and 5s5f have been newly worked out to almost completeness. The total number of the known energy levels of Zr III is now 137 including 41 levels freshly added. We derive from nd series the ionization energy of Zr III to be 186 400 ± 500 cm-1 (23.11 ± 0.06 eV).

Extended Analysis of Mo VI

The analysis of the RbI-like spectrum Mo VI has been extended to include a total of some 110 classified lines and 44 energy levels belonging to the one-electron configurations 4s24p6(1S) nl with n ranging up to 9 and l up to 7. The analysis is based on recordings of vacuum spark spectra made at Lund in the region 230-2350 A, complemented by a list of lines from 2193 to 6336 A observed and identified by Romanov and Striganov in a Penning type arc discharge. The one-electron level system is partly mixed with core-excited configurations, not treated in the present paper. Especially the nf series is strongly perturbed by 4s24p54d2, and an anomalous behaviour of the ng series is explained by interaction with the 2G term of 4s4p64d2. The ionization limit, derived from 6h, 7i and 8k by means of the polarization formula, is found to be 555 132 ± 2 cm-1.

Addition to the analysis of Y VII, VIII and Mo X

With the help of newly recorded spectrograms, the seven hitherto unknown levels of the 4p24d configuration of Y VII and Mo X have been determined, and three previously reported level values of Y VII are improved upon. Eight new levels of 4s4p3 of Y VIII are added to the only two of this configuration which were already known. This completes the structural knowledge of the four lower configurations of Y VIII, namely 4s24p2, 4s4p3, 4s24p4d and 4s24p5s.

Transitions between excited energy levels of Zr VII

Based on the spectrograms recorded at Lund University, 249 newly classified lines of six times ionised zirconium atoms (Zr VII) are reported. All the 38 energy levels of the 4p34d configuration along with 24 of the 4p35p and 39 of the 4p34f configurations are now established through the transitions 4p4-4p34d, 4p3(4d-4f, 5p) and 4p3(5s-5p) which lie in the wavelength region 290-2500 AA.

Classified Lines and Energy Levels of Mo V

An extensive analysis of the fifth spectrum of molybdenum is described, based on Lund recordings. We report 535 classified lines connecting 141 energy levels, of which 122 are new. The structure of the configurations 4s24p64d2, 4d5s, 4d6s, 4d5p, 4d6p, 4d5d, 4d6d, 4d4f, 4d5f, 5s2, 5s6s, 5s5p, 5s6p, 5s5d, 5s4f and 5p2 is now completely known. The ionization energy of Mo V is derived to be 435700 ± 300 cm-1 (53.98 ± 0.04 eV).

Spectrum of Five Times Ionized Zirconium (Zr VI)

We report 279 newly identified transitions of five times ionized zirconium atom (Zr VI) based on recordings made at the 3 m normal incidence spectrograph of Lund University. Thirty-three new energy levels have been established, comprising all the twenty-one levels of 5p configuration, all the nine of 4d that were not known so far, and three of 7s. Previously reported values of one 5d and four 6s levels have been improved. The sixth ionization potential of zirconium 4p5 2P3/2 -4p4 3P2 is reevaluated from smooth ns Rydberg series to be 776 500 ± 500 cm-1 which corresponds to 96.21 ± o.06 eV. Latest isoelectronic situation of 4p56s levels is presented.

Additions to the Spectrum of Quadruply Ionized Zirconium (Zr V)

Based on spectrograms recorded for the region 250-2550 A on the 3 m normal incidence spectrograph of Lund University, we have classified 358 lines, including 164 newly identified ones, as transitions between levels of excited configurations of Zr V. These classifications led us to establish 35 new energy levels belonging to the 4s24p56p, 7p, 5f and 6f configurations and to confirm energy levels of the configurations 4s24p5ns (n = 5-10), 5p, 4d, 5d, 4f, 5g, 6g and 4s4p64d reported by Reader and Acquista.

Spectrum of Trebly Ionized Zirconium (Zr IV)

The zirconium spectrum is recorded on the 3 m normal incidence spectrograph of the Physics Department, Lund University; analysis of Zr IV is revised and extended. Identification of thirty-four 4p6 nd-4p5 4d2 (n = 4, 5, 6) transitions led to establish twelve 4p5 4d2 levels. Fifteen transitions are added to the analysis of the one-electron spectrum, establishing 7p levels and revising 6d.