Z. A. Khan

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).

ANALYSIS OF p-4, 6, 8He AND p-6, 9, 11Li SCATTERING

Using the Coulomb modified Glauber model, we analyze the elastic scattering of protons from He and Li isotopes at 60 MeV and 72 MeV. The calculations require two inputs; the nucleon–nucleon (NN) amplitude and the nucleon density distributions in target nuclei. The central part of the NN amplitude is taken from the available NN scattering observables. To find the spin-dependent part, we employ p-4He scattering data to fix its parameter values. For target nuclei, we use nucleon density distributions available in the literature. The NN amplitude, as obtained in this work, is then used to study the sensitivity of the calculated differential cross-section and polarization for p-6, 8He scattering on the density distributions used. It is found that both the differential cross-section and polarization could provide a test to know which is the better choice of nucleon (especially neutron) density distributions. We also present the differential cross-sections for p-6, 9, 11Li scattering at 60 MeV and 72 MeV in order to assess the suitability of the obtained NN amplitude. It is found that the results are in reasonable agreement with the experiment up to only moderate scattering angles, leaving significant discrepancy at large scattering angles. Our calculations suggest the need of medium modifications in the NN amplitude, arising due to Pauli blocking.

16O-NUCLEUS ELASTIC SCATTERING IN THE ENERGY RANGE 300 MeV–1.503 GeV

In this work we analyze the elastic angular distribution for the scattering of 16O from 12C, 16O, 28Si, 40Ca, 90Zr, and 208Pb in the energy range 300 MeV–1.503 GeV within the framework of the Coulomb modified correlation expansion for the Glauber amplitude. Our calculations involve (i) up to the two-body density term in the correlation expansion, (ii) the realistic nuclear form factors, and (iii) the high q-components of the basic (input) NN amplitude. The results are found to provide a satisfactory explanation of the data in all the cases. Moreover, we could assess the energy dependence of the NN amplitude, and the trend of its slope strengthens the need of nondiffractive behavior of the NN amplitude in the energy range under consideration. We also show that the c.m. correlations play an important role in nucleus–nucleus collision.

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.

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.

4s24p2-4s4p3 transitions in Zr IX

Twenty five 4s24p2-4s4p3 transitions are identified in Zr IX establishing all the ten 4s4p3 levels of this spectrum, recorded on the 3m normal incidence vacuum spectrograph of Lund University.

Resonance transitions in Zr VIII

The zirconium spectrum produced in a condensed vacuum spark source was recorded on the 3 m normal-incidence spectrograph of the physics department, Lund University (Sweden) from about 250-2550 AA, using aluminium and gold coated gratings. Thirty lines are classified as 4s24p3-4s4p4 transitions, establishing all eight 4s4p4 levels of Zr VIII. New identification of 18 4s24p3-4s24p24d transitions led the authors to determine seven more 4p24d levels, thus completing the knowledge of this configurations structure except for (3P)4F9/2 and (1D)2G9/2 that do not combine with the ground levels.

α-nucleus elastic scattering at 240–480 MeV

Working within the framework of the Glauber model, we analyze the elastic angular distribution for the scattering of α particles from 58Ni, 90Zr, 116Sn and 208Pb at 240, 288, 340 and 480 MeV. Instead of using the conventional (one-term) Gaussian parameterization for the basic (input) nucleon–nucleon (NN) amplitude, we involve that form of an NN amplitude which may be used for a wide range of angles. This work requires an NN amplitude at 60, 72, 85 and 120 MeV. Using the realistic form factors for the colliding nuclei, it is found that the results strongly support the need for higher momentum transfer components of the NN amplitude to provide a satisfactory account of the experimental data, particularly in the region of large scattering angles. The analysis also provides the behavior of the NN amplitude beyond 70 MeV, not obtained earlier. Moreover, we note that the phenomenological treatment of the medium effects, relating Pauli blocking, provides an overall better description of the data in all the cases.