Angular distributions of electrons in photoionization of 3s subshell of atomic chlorine

R-matrix calculated photoelectron angular distribution asymmetry parameters, beta for Cl+ 3s3p(5) P-3(o) and 3s(2)3p(3) (D-2(o))3d P-1(o) final ionic states in photoionization of the ground state of atomic Cl are presented in the photon energy range from threshold to 80 eV. The results, characterized by prominent autoionization structures which are sensitive to multielectron correlations, are compared with those recently measured by Whitfield et al (Whitfield S B, Kehoe K, Krause M 0 and Caldwell C D 2000 Phys. Rev. Lett. 84 4818). Contrary to experiment and previous theoretical calculations, our detailed CIV3 structure calculation (Deb N C, Crothers D S F, Felfli Z and Msezane A Z 2002 J. Phys. B: At. Mol. Opt. Phys. submitted) has identified the lowest P-1(o) level of Cl+ as 3S(2)3p(3)(D-2(o))3d P-1(o) rather than 3s3p(5) P-1(o). The implications and consequences of the measured data for the 3s P-1(o) level are also discussed in the context of our calculated energies for Cl+ and beta for 3d P-1(o).

Nuclear structure effects in internal conversion

Experimental studies of nuclear effects in internal conversion in Ta¹⁸¹ and Lu¹⁷⁵ have been performed. Nuclear structure effects (“penetration” effects), in internal conversion are described in general. Calculation of theoretical conversion coefficients are outlined. Comparisons with the theoretical conversion coefficient tables of Rose and Sliv and Band are made. Discrepancies between our results and those of Rose and Sliv are noted. The theoretical conversion coefficients of Sliv and Band are in substantially better agreement with our results than are those of Rose. The ratio of the M1 penetration matrix element to the M1 gamma-ray matrix element, called λ, is equal to + 175 ± 25 for the 482 keV transition in Ta¹⁸¹ . The results for the 343 keV transition in Lu¹⁷⁵ indicate that λ may be as large as – 8 ± 5. These transitions are discussed in terms of the unified collective model. Precision L subshell measurements in Tm¹⁶⁹ (130keV), W¹⁸² (100 keV), and Ta¹⁸¹ (133 keV) show definite systematic deviations from the theoretical conversion coefficients. The possibility of explaining these deviations by penetration effects is investigated and is shown to be excluded. Other explanations of these anomalies are discussed.

Gound State Properties of Nuclei in (295)118 alpha-Decay Chain

The properties of nuclei belonging to the alpha-decay chain of superheavy element (295)118 have been studied in the framework of axially deformed relativistic mean field (RMF) theory with the parameter set of NL-Z2 in the blocked BCS approximation. Some ground state properties such as binding energies, deformations, and alpha-decay energies Q(alpha) have been obtained and agree well with those from finite-range droplet model (FRDM). The single-particle spectra of nuclei in (295)118 alpha-decay chain show that the shell gaps present obviously nucleon number dependence. The root-mean-square (rms) radii of proton, neutron and matter distributions change slowly from (283)112 to (295)118 but dramatically from (279)110 to (283)112, which may be due to the subshell closure at Z = 110 in (279)110. The alpha-decay half-lives in (295)118 decay chain are evaluated by employing the cluster model and the generalized liquid drop model (GLDM), and the overall agreement is found when they are compared with the known experimental data. The alpha-decay lifetimes obtained from the cluster model are slightly larger than those of GLDM ones. Finally, we predict the alpha-decay half-lives of Z = 118, 116, 114, 112 isotopes using the cluster model and GLDM, which also indicate these two models can corroborate each other in studies on superheavy nuclei. The results from GLDM are always lower than those obtained from the cluster model.

20—50MeV O5+离子引起Au的L壳层X射线产生截面研究

在北京13 MV串列加速器上利用20—50MeV O5+离子研究Au的L壳层X射线产生截面. 实验结果表明σ（Ll）/σ（Lα） ，σ（Lβ）/σ（Lα） 和σ（Lγ）/σ（Lα）与EＣＰSSR理论计算结果符合比较好.在实验中由于较高的能量,在能量点存在能移现象.

Photoionization of 1s electron and corresponding shake-up process in ground and excited lithium atoms

The cross sections of the 18 electron photoionization and corresponding shake-up processes for Li atoms in the ground state 1s(2)2s and excited states 1s(2)2p, 1s(2)3p, 1s(2)3p and 1s(2)3d are calculated using the multi-configuration Dirac-Fock method. The latest experimental photoelectron spectrum at hv = 100 eV [Cubaynes D et al. Phys. Rev. Lett. 99 (2007) 213004] has been reproduced by the present theoretical investigation excellently. The relative intensity of the shake-up satellites shows that the effects of correlation and relaxation become more important for the higher excited states of the lithium atom, which are explained very well by the spatial overlap of the initial and final state wavefunctions. In addition, strong dependence of the cross section on the atomic orbitals of the valence electrons are found, especially near the threshold.

beta-delayed proton decays and spin assignments for Tb-140, Dy-141 and Dy-143

The proton-rich isotopes Tb-140 and Dy-141 were produced via the fusion evaporation reaction Ca-40+ Cd-106. Their beta-delayed proton decays were studied by p-gamma coincidence in combination with a He-jet tape transport system, and half-lives, proton energy spectra, gamma-transitions following the proton emission, as well as beta-delayed proton branching ratios to the low-lying states in the grand-daughter nuclei were determined. Comparing the experimental data with statistical model calculations, the ground-state spins of Tb-140 and Dy-141 were found to be consistent with 7 and 9/2, respectively. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated using the Woods-Saxon-Strutinsky method, which suggest the ground-state spins and parities of Tb-140 and Dy-141 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 were calculated, which predict a 1/2(+) ground state and a 11/2(-) isomer with excitation energy of 198 keV. These findings are consistent with our previous experimental data on Dy-143 reported in Eur. Phys. J. A 16, 347 (2003).

Rotation alignment in neutron-rich Cr isotopes: A probe of deformed single-particle levels across N=40

Recent experiments have reached the neutron-rich Cr isotope with N = 40 and confirmed enhanced collectivity near this subshell. The current data focus on low-spin spectroscopy only, with little information on the states where high-j particles align their spins with the system rotation. By applying the projected shell model, we show that rotation alignment occurs in neutron-rich even-even Cr nuclei as early as spin 8 (h) over bar h and, owing to shell filling, the aligning particles differ in different isotopes. It is suggested that observation of irregularities in moments of inertia is a direct probe of the deformed single-particle scheme in this exotic mass region.

Au LX射线发射截面和Al、Ti、Ni表面可见、红外光谱测量

本实验工作是在中国原子能科学研究院的HI-13串列加速器国家实验室第二测量厅原子物理实验平台上完成。本工作采用能量为20-50MeV的高电荷态O5+离子去轰击Au, 测量了不同能量下Au的L1、Lα、Lβ、Lγ的X射线谱，计算了不同能量下各条X射线的产生截面，并与ECPSSR理论计算结果进行了比较。实验结果表明σ（Ll）/σ(Lα) 和σ（Lγ）/σ(Lα)与ECPSSR理论计算结果符合比较好，而对于σ（Lβ）/σ(Lα)，在较低能区实验值略高于理论值。在中国科学院近代物理研究所320kV高电荷态离子实验研究平台上测量了Xeq+ (q=17-29)入射Al、Ti和Ni等表面诱发的可见光和红外光。通过对靶原子光谱线的研究，实验发现，随着入射离子的电荷态增高，原子和离子的各种光谱线可得到有效地激发。低速高电荷态离子入射金属固体表面，靶原子的特征谱线的激发强度，与入射离子的电荷态q密切相关。qc的实验测量值和理论计算值符合的较好

Two-Photon Inner-Shell Ionization in the Extreme Ultraviolet

We have observed the simultaneous inner-shell absorption of two extreme-ultraviolet photons by a Xe atom in an experiment performed at the short-wavelength free electron laser facility FLASH. Photoelectron spectroscopy permitted us to unambiguously identify a feature resulting from the ionization of a single electron of the 4d subshell of Xe by two photons each of energy (93 +/- similar to 1) eV. The feature's intensity has a quadratic dependence on the pulse energy. The results are discussed and interpreted within the framework of recent results of ion spectroscopy experiments of Xe obtained at ultrahigh irradiance in the extreme-ultraviolet regime.

Oscillator strengths and transition probabilities for the W xlv ion

In this paper we present oscillator strengths and transition probabilities for W xlv transitions between levels arising from configurations 3d¹⁰4s²,4p²,4d², 3d¹⁰4k4l (k = s,p,d,f and l = p,d,f), 3d⁹4s²4l (l = p,d,f) and 3d⁹4s4p². The model used to calculate these contained all configurations which can be constructed from the available orbitals (up to n = 4), with either a 3d¹⁰ or 3d⁹ core. The calculations were performed with the configuration interaction CIV3 program with the inclusion of relativistic effects achieved through the use of the Breit-Pauli approximation. We compare our ab initio energy levels, oscillator strengths and transition rates with other experimental and theoretical values available in the literature. There is generally good agreement when only levels with 3d¹⁰ cores are considered. The literature is sparse for levels in which the 3d-subshell is opened: for the majority of the fine-structure lines considered, there is either no comparison data available or substantial differences are found. This paper also investigates how the inclusion of relativistic effects can result in a significant redistribution of the oscillator strength from the LS calculations.

Electron-impact ionization of Al2+

We report on a nonperturbative R-matrix with PseudoStates (RMPS) calculation for the electron-impact ionization cross section of the ground state of Al2+. We include both the direct ionization of the 3s and 2p subshells and the indirect ionization from the 2p subshell. This calculation, thus, includes extra decay channels for the indirect-ionization process not included in previous RMPS calculations. This lowers the total-ionization cross section, resulting in closer agreement with the most recent experimental measurements. This calculation also shows better agreement with the position and height of the resonant-excitation double autoionization features seen in the experiment.

Dielectronic recombination of W 35 +

Accurate data for dielectronic recombination (DR) of the ions of tungsten are of significant interest in the modelling of tungsten impurity transport and radiative power loss in current tokamaks and in ITER. However, the complexity of the atomic structure for many of these ions makes level-resolved DR calculations untenable on currently available computers, especially for open d- and f-subshell ions. The majority of DR data presently available for ITER modelling are based on an average-atom approximation. To improve upon these baseline calculations, we investigate the use of the configuration-average distorted-wave (CADW) method to calculate DR rate coefficients for complex open d-shell systems. The aim is to produce rate coefficients that are sufficiently accurate in terms of modelling, yet greatly reduced in term of computational complexity compared to level-resolved calculations. In this paper, we consider the DR of W 35 + . Initially, we carry out several large-scale level-resolved calculations for the DR associated with the 4d → 4f and 4p → 4d excitations in this ion, using both the level-resolved distorted-wave and Dirac R -matrix methods. These calculations allow us to test the validity of the CADW approach on these same excitations by comparing cross sections and rate coefficients. These comparisons demonstrate that the CADW method is relatively accurate in relation to these level-resolved methods for the temperature range for which W 35 + should exist in a collisionally ionized plasma. We then present results for CADW rate coefficients for both Δ n = 0 and Δ n = 1 excitations for this ion. This study indicates that it is now feasible to generate a much improved comprehensive set of DR data for the entire tungsten isonuclear sequence.

Efeito fotocrômico em Ormosil's dopados com molibdênio preparados por síntese de Sol-Gel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Kollineare Laserspektroskopie an radioaktiven Praseodymionen und Cadmiumatomen

Die Analyse optischer Spektren liefert einen kernmodellunabhängigen Zugang zur Bestimmung der Kernspins, Ladungsradien und elektromagnetischen Momente von Atomkernen im Grundzustand und von langlebigen Isomeren. Eine der vielseitigsten Methoden zur optischen Spektroskopie an kurzlebigen Isotopen ist die kollineare Laserspektroskopie. Im Rahmen dieser Arbeit wurde zum einen die TRIGA-LASER Strahlstrecke am Institut für Kernchemie der Universität Mainz durch die Implementierung einer neuen offline Oberflächenionenquelle für hohe Verdampfungstemperaturen und eines Strahlanalysesystems weiterentwickelt. Zum anderen wurde kollineare Laserspektroskopie an kurzlebigen Praseodym- und Cadmiumisotopen an ISOLDE/CERN durchgeführt. Die neue Ionenquelle ermöglichte dabei den Test der kollinearen Laserspektroskopie an Praseodymionen am TRIGA-LASER Experiment. Die Spektroskopie der Prasdeodymionen motivierte sich aus der Beobachtung einer zeitlichen Modulation der EC-Zerfallsrate von wasserstoffähnlichem 140Pr58+. Für die Erklärung dieser sogenannten GSI Oszillationen wird unter anderem das magnetische Moment des Kerns benötigt, welches bislang noch nicht experimentell bestimmt wurde. Zudem wurde für wasserstoffähnliches 140Pr58+ überraschenderweise eine kleinere EC-Zerfallskonstante gemessen als für heliumähnliches 140Pr57+. Die Erklärung dieses Phänomens setzt ein positives magnetisches Moment voraus. Bei der Spektroskopie am COLLAPS Experiment wurden erstmals die magnetischen Momente von 135Pr, 136Pr und 137Pr vermessen. Aufgrund zu geringer Produktionsraten war die Spektroskopie des gewünschten Isotops 140Pr jedoch nicht erfolgreich. Die Untersuchung der Cadmiumisotope ist kernphysikalisch motiviert. In der Zinnregion erstrecken sich die Isotope über die beiden magischen Zahlen N=50 und N=82 bei gleichzeitiger Nähe des Z=50 Schalenabschlusses. Hier können verschiedene Kernmodelle getestet werden, die sich beispielsweise hinsichtlich der Stärke des N=82 Schalenabschlusses widersprechen. Diese Arbeit berichtet über erste Ergebnisse der Spektroskopie an Cadmiumatomen, die sich über die Isotope 106−124,126Cd sowie die zugehörigen langlebigen I=11/2− Isomere erstreckt. Die zuvor experimentell bekannten oder aus dem erweiterten Schalenmodell abgeleiteten Kernspins konnten für alle Isotope bis auf 119Cd bestätigt werden. Der Kernspin von 119Cd wurde eindeutig zu I=1/2 bestimmt. Die elektrischen Quadrupolmomente der Isomere zeigen ein bemerkenswert lineares Verhalten in Abhängigkeit von der Neutronenzahl und dies über die eigentliche Kapazität der 1h11/2 Unterschale hinaus. Die Änderungen der mittleren quadratischen Ladungsradien zeigen den auch an Indium- und Zinnisotopen beobachteten stetigen Verlauf. Der lineare Anteil passt sehr gut zu den Berechnung des Tröpfchenmodells in der Parametrisierung nach Berchidevsky und Tondeur. Die Differenzen der mittleren quadratischen Ladungsradien zwischen Grund- und isomeren Zustand der ungeraden Cadmiumisotope zeigen einen interessanten parabolischen Verlauf mit einem Minimum zwischen A=117 und A=119.

A new set of relativistic screening constants for the screened hydrogenic model

AnewRelativisticScreenedHydrogenicModel has been developed to calculate atomic data needed to compute the optical and thermodynamic properties of high energy density plasmas. The model is based on anewset of universal screeningconstants, including nlj-splitting that has been obtained by fitting to a large database of ionization potentials and excitation energies. This database was built with energies compiled from the National Institute of Standards and Technology (NIST) database of experimental atomic energy levels, and energies calculated with the Flexible Atomic Code (FAC). The screeningconstants have been computed up to the 5p3/2 subshell using a Genetic Algorithm technique with an objective function designed to minimize both the relative error and the maximum error. To select the best set of screeningconstants some additional physical criteria has been applied, which are based on the reproduction of the filling order of the shells and on obtaining the best ground state configuration. A statistical error analysis has been performed to test the model, which indicated that approximately 88% of the data lie within a ±10% error interval. We validate the model by comparing the results with ionization energies, transition energies, and wave functions computed using sophisticated self-consistent codes and experimental data.