First observation of atomic levels for the element fermium (Z=100)

The atomic level structure of the element fermium was investigated for the first time using a sample of 2.7x10(10) atoms of the isotope 255Fm with a half-life of 20.1 h. The atoms were evaporated from a filament and stored in the argon buffer gas of an optical cell. Atomic levels were sought by the method of resonance ionization spectroscopy using an excimer-dye-laser combination. Two atomic levels were found at wave numbers (25 099.8+/-0.2) and (25 111.8+/-0.2) cm(-1). Partial transition rates to the 5f(12)7s(2) (3)H(e)(6) ground state have been determined from their saturation characteristics. Multiconfiguration Dirac-Fock calculations suggest that the leading orders of these levels could be the 5f(12)7s7p (5)I(o)(6) and 5f(12)7s7p (5)G(o)(5) terms.     

The ignored discovery of the element Z = 43

Until now Perrier and Segrè (Palermo, 1937) are credited for the first observation of the element Z = 43, called technetium (Tc). We give arguments for the statement that Walter Noddack, Ida Tacke and Otto Berg (Berlin, 1925) should be credited for the discovery of this element. In their search for the missing eka-manganese elements with Z = 43 and Z = 75 they observed the X-rays of these elements, with the peculiar behaviour though that the Z = 43 lines only appeared in ores, quoted to contain percentage quantities of uranium. The presence of element Z = 43 in uraniumcontaining ores can now be explained through the long-living fission product ⁹⁹43 in their samples; they proposed the names masurium (Ma) and rhenium (Re) for the discovered elements. By reanalysing the original experimental conditions, we conclude that the detection limit for their observing the X-rays of Z = 43 can be 1000 times lower than the 10⁻⁹ detection limit for the element Z = 75. This brings us very close to the expected abundance of Z = 43 in the analysed samples, such that we do not see reasons for questioning the credibility of the experimental evidence.     

On evaporation residue cross sections producing nuclei with Z=104−120

A phenomenological method to predict the evaporation residue cross section in the superheavy mass region is presented. It makes us possible to understand what are the main contributors to the cross section and to perform a systematic analysis for understanding the fusion-fission mechanism by finding a deviation from the average property by means of this method.     

Theoretical predictions on cluster radioactivity of superheavy nuclei with Z = 119, 120

In this study,we investigate the cluster radioactivity(CR) of new superheavy elements with Z=119 and120 based on two successful theoretical methods with modified parameters:the density-dependent cluster model(DDCM) and unified decay formula(UDF).First,we employ the DDCM and UDF to accurately reproduce the experimental half-lives of cluster emissions,which demonstrates the high reliability of our theoretical methods.Then,we systematically predict the probable cluster modes of ^293-311 1...     

1.06μm激光等离子体软X射线辐射及对原子序数的依赖

详细地研究了1.06μm激光等离子体X光的辐射特性;分析了不同谱带发射强度对激光能量的依赖关系,并给出了K、L、M、N、O谱带发射强度对原子序数的依赖关系.     

Effective atomic number and density determination of rocks by X-ray microtomography

Microtomography, as a non-destructive technique, has become an important tool in studies of internal properties of materials. Recently, interest using this methodology in characterizing the samples with respect to their compositions, especially rocks, has grown. Two physical properties, density and effective atomic number, are important in determining the composition of rocks. In this work, six samples of materials with densities that varied from 2.42 to 6.84 g/cm³ and effective atomic numbers from 15.0 to 77.3 were studied. The measurements were made using a SkyScan-Bruker 1172 microtomography apparatus operating in voltages at 50, 60, 70, 80, 90 and 100 kV with a resolution of 13.1 μm. Through micro-CT images, an average gray scale was calculated for the samples and correlation studies of this value with the density and the effective atomic number of samples were made. Linear fits were obtained for each energy value. The obtained functions were tested with samples of Amazonite, Gabbro, Sandstone and Sodalite.     

Decay properties of neutron-deficient isotopes of elements from Z = 101 to Z = 108

In a series of experiments performed at the velocity filter SHIP, new or improved decay data of neutron-deficient isotopes of elements from mendelevium (Z = 101) to hassium (Z = 108) were obtained. In particular, evidence for -decay or electron capture from isomeric states in ²⁶⁵Hs and ²⁵⁸Db was found.     

The X-ray emission from the knots in 3C 120

3C 120 is a Seyfert galaxy with a well detected X-ray jet. We investigate the X-ray emission of its five jet knots and fit their spectral energy distributions (SEDs) from the radio to the X-ray bands with a single-zone lepton model. We find that the SEDs of knots k7, s2, and s3 can be explained by synchrotron radiation, and the X-rays are the simple extension of the radio-optical emission component, but that of the inner knot k4 requires the IC/CMB model, in which the X-rays are due to the inverse Compton scattering of the cosmic microwave background photons by relativistic electrons in the jet with a beaming factor δ∼14. The outer knot k25 is resolved into a three-part sub-structure. It is shown that the fitting of the X-rays from this knot with the IC/CMB model needs an extraordinary beaming factor δ∼15–25 for a jet at the kpc scale. If the X-rays of knot k25 are produced by synchrotron radiation similar to k7, s2, and s3, they may be contributed by a relativistic electron population whose radiations in other wavelengths are not detected.

     

X-ray emission from highly stripped atomic ions

Relativistic Dirac-Fock (DF) and central-field Dirac-Fock-Slater (DFS) calculations of X-ray emission from highly stripped atomic lead ions have been performed. The X-ray line shifts provide a nonmonotone characteristic of outer-shell ionization. The intensities of the most intense X-ray lines are largely unaffected by the removal of outer-shell electrons.     

X-ray spectroscopy from variable,Z laser-produced plasmas

We have investigated the sensitivity of X-ray line intensities as a laser-plasma diagnostic by seeding Si in CH and PbO plasmas. The Si K X-ray spectrum is measured using both time-integrating and time-resolving spectrographs to investigate the effect of time averaging on the line intensities. The measured intensities are compared with theoretical estimates for an isothermal, isodensity plasma. Si line intensities vary with the Z of the plasma, as expected from simple scaling models, indicating the Si lines can be a good plasma diagnostic. The line intensities do not predict a unique temperature and density, but, instead, the inferred temperature and density vary, depending on the line ratio used. These variations are attributed to large spatial gradients of temperature and density in the plasmas. Problems in interpretation are discussed, as well as possible directions for future experiments.     

Radiative strength functions for nuclei in which the number of protons is close to the magic number of Z=28

The distribution of the radiative strength in nuclei where the number of nucleons of one type is nearly magic (Z=28±1) and where there are a few valence nucleons of the other type is investigated. It is shown that the statistical approach that is based on Fermi liquid theory and which takes into account temperature and the shell structure of nuclei leads to good agreement with experimental data on radiative strength functions below the neutron binding energy in such nuclei. Only for the ⁵⁹Co and ⁶⁵Cu nuclei, which have the largest number of valence neutrons among the cobalt and copper isotopes being investigated, is the energy dependence of the radiative strength compatible with a Lorentz distribution as well.     

Local variations of charge radii for nuclei with even Z from 84 to 120

Pronounced changes of nuclear charge radii provide a stringent benchmark on the theoretical models and play a vital role in recognizing various nuclear phenomena. In this work, the systematic evolutions of nuclear charge radii along even Z = 84–120 isotopic chains are first investigated by the recently developed new ansatz under the covariant density functional. The calculated results show that the shell closure effects of nuclear charge radii appear remarkably at the neutron numbers N = 126 and...     

N=Z原子核性质的研究

论述了N=Z核实验和理论研究的历史和现状在,N=Z,是研究T=0对关联最好的核区,实验表明T=0和n-p对关联起着重要的作用,理论研究知心朋友同时包括T=0和T=1的对关联,是研究它们之间竞争及相变。 The history and current status of the study of N=Z nuclei are reviewed. T=0 n p pairing correlation is expected to play an important role in the structure of the nuclei along N=Z line. Both T=0 and T=1 pairing modes should be included in the theoretical models. Phenomena like possible competition and phase transition between different pairing modes are becoming important issues in nuclear structure.     

超重元素Bh（Z=107）的激发态结构和共振吸收率的理论预言

在成功预言了100号元素Fm低激发态能级结构的基础上，通过系统考虑电子相关效应和相对 论效应，使用MCDF方法进一步预言了107号元素Bh的几个较低的激发态能级以及由基态到这 些激发态的共振吸收率.期望预言的结果会对进一步的实验工作提供一定的帮助. 关键词： 超重元素 MCDF方法 低激发态结构     

Plastic plasma interaction with plasmas with growing atomic number

This paper describes the investigation of the influence of target material atomic number (Z) on the laser-produced plasma pressure. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5 - 73), i.e. plastic (CH), Al, Cu, Ag, and Ta, were used. The results presented show that the plasma pressure decreases with growing atomic number but in a limited range of Z only. For higher Z, starting approximately from Z = 47 (Ag), the plasma pressure becomes constant, as confirmed by interferometric measurements and x-ray plasma imaging.