Half-lives and fine structure for the α decay of deformed even-even nuclei

The α-decay properties of well-deformed even-even nuclei are systematically calculated within the multichannel cluster model (MCCM). Instead of working in the WKB framework, the quasibound solution to the coupled Schro¨dinger equation is presented with outgoing wave boundary conditions, and the coupling potential is taken into full account in terms of the general quantum theories. The calculated α-decay half-lives are found to agree well with the experimental data with a mean factor of less than 2. The fine...     

Fine structure ofαdecay in222Pa

With the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system,the fine structure of the α decay for²²²Pa was studied.The nuclides were produced through the 1p3n evaporation channel via the heavy-ion induced fusion evaporation reaction ⁴⁰Ar+¹⁸⁶W.Based on the ER-α1-α2-α3 andα-γcorrelation measurement,three new α decays were observed in addition to the three branches known previously.The one with the largestαdecay energy was regarded as the ground state to ground state transition.The newly measuredαdecay properties of ²²²Pa were examined in a framework of reduced width.     

Charge distribution of the daughter atom in α decay of 210Po

The evaporation model developed by Russek and collaborators for multiple ionization of outer-shell electrons in ion-atom collisions has been applied to the charge distribution of the daughter atom produced by α decay of ²¹⁰Po. The calculated result indicates that most of the daughter atoms are positively charged ions with a mean charge of + 1.41. The other ionization mechanisms, the recoil effect and the shake-off effect, are also considered. In comparison with the recent experimental results, it is shown that the evaporation model predicts more adequately than the recoil effect and the shake-off effect.     

Polarization bremsstrahlung in α decay

A mechanism of formation of electromagnetic radiation that accompanies α decay and is associated with the emission of photons by electrons of atomic shells due to the scattering of α particles by these atoms (polarization bremsstrahlung) is proposed. It is shown that, when the photon energy is no higher than the energy of K electrons of an atom, polarization bremsstrahlung makes a significant contribution to the bremsstrahlung in α decay.     

Hyperfine structure and isotope shift investigations in202–222Rn for the study of nuclear structure beyond Z=82

The hyperfine structure (hfs) and isotope shift (IS) in the isotopic chain of the radioactive element radon have been studied for the first time. The measurements were carried out by collinear fast-beam laser spectroscopy at the mass separator facility ISOLDE at CERN. The IS between 16 isotopes in the mass range 202A222 and the hfs of 7 odd-A isotopes were determined in the transitions 7s [3/2]₂-7p [5/2]₃ (745 nm) of Rn I. The nuclear spins and moments, as well as the observed inversion of the odd-even staggering for^218–222Rn, can be associated with the effects of octupole instability around N=134.This work was supported by the Bundesministerium für Forschung und Technologie and the Deutsche Forschungsgemeinschaft.     

X-ray diffraction studies of specific features in the atomic structure of Fe-Si alloys in the α area of the phase diagram

The atomic structure of Fe-Si alloys with a silicon concentration of 5–8 at % (α-area of the phase diagram) was studied using X-ray diffraction. The effect of quenching after annealing at a disordering temperature of 850°C on the structural state of the alloys was elucidated. It is shown that the quenched samples are characterized by a short-range ordering; namely, there is a local B2-type order at a concentration of 5–6 at % Si and, in addition, DO₃-phase clusters are formed at 8 at % Si. The atomic structure of B2 clusters and their nearest surroundings is established.     

Fine structure in the α-decay of radium isotopes with mass numbers 209-212

Radium isotopes with mass numbers from 209 to 212 have been produced by heavy-ion fusion reactions ²⁰⁴Pb( ¹²C, xn) ^216-Ra. Radioactive decay properties were investigated by means of α- and α-γ-spectroscopy after in-flight separation of the evaporation residues from the projectile beam by the velocity filter SHIP and implantation into a 16-strip position-sensitive Si detector. For the even-even nuclei ^210,212Ra we identified α transitions into the first-excited 2⁺-state of the daughter nuclei ^206,208Rn. Weak α transitions into excited levels of the odd-A daughter nuclei ^205,207Rn were also observed. Received: 19 August 2002 / Accepted: 6 November 2002 / Published online: 18 February 2003 RID="a" ID="a"e-mail: f.p.hessberger@gsi.de Communicated by D. Guerreau     

Fine structure and inverse population in the MnKβ1 spectra of MnxZnyFezO4 ferrites

The electronic structure of Mn_xZn_yFe_zO₄ single-crystal ferrites was investigated. The fine structure of their X-ray spectra was found to correlate with the populations of quantum states. A scheme is suggested for the evolution of the electronic structure with strengthening exchange interaction of valence electrons as the chemical composition of the system becomes more complex. The metal-insulator phase transition is possible in the range of compositions corresponding to densities from ρ=5.097 g/cm³ to ρ=5.125 g/cm³, where manganese changes its charge state.     

On the possibility of accelerating α decay: To the problem of disposing of radioactive nuclear waste

A number of experimental tests of the recent information on the possibility of accelerating α decay by implanting α-emitting isotopes into metals with their further cooling to a low temperature were performed using the nuclear orientation technique. The measurement data on half-lives for ²⁵³Es in Fe at 4 K and 50 mK, ²²⁴Rn, ²²⁵Ra, and ²²⁷Ac in Fe at temperatures down to 25 mK, and ²²¹Fr in nonmetal (Si) and metal (Au) at 4 K and ∼20 mK are reviewed. In all cases, no change in half-life was found within an accuracy of 1%.     

Fine and hyperfine structure in the X2Σ+ state of gas-phase yttrium monoxide

The A²Π_r-X²Σ⁺ visible spectrum of gas-phase yttrium monoxide has been studied at sub-Doppler resolution to obtain information on the spin-rotation and ⁸⁹Y nuclear magnetic hyperfine interactions. The observations were fitted to an effective Hamiltonian model that neglected the nuclear magnetic hyperfine interactions in the excited electronic state. An interpretation of the determined parameters in terms of possible electronic configurations is presented.     

Fine structure of the isoscalar giant quadrupole resonance in Ca due to Landau damping?

The fragmentation of the Isoscalar Giant Quadrupole Resonance (ISGQR) in ⁴⁰Ca has been investigated in high energy-resolution experiments using proton inelastic scattering at Ep=200 MeV$E_{\mathrm{p}}=200\text{MeV}$. Fine structure is observed in the region of the ISGQR and its characteristic energy scales are extracted from the experimental data by means of a wavelet analysis. The experimental scales are well described by Random Phase Approximation (RPA) and second-RPA calculations with an effective interaction derived from a realistic nucleon–nucleon interaction by the Unitary Correlation Operator Method (UCOM). In these results characteristic scales are already present at the mean-field level pointing to their origination in Landau damping, in contrast to the findings in heavier nuclei and also to SRPA calculations for ⁴⁰Ca based on phenomenological effective interactions, where fine structure is explained by the coupling to two-particle–two-hole (2p–2h) states.     

Effects of shell correction on α decay properties

The shell correction effects on the α decay properties of heavy and superheavy nuclei have been studied in a macroscopic-microscopic manner. The macroscopic part is constructed from the generalized liquid drop model(GLDM), whereas the microscopic part, namely, the shell correction energy, brings about certain effects on the potential barriers and half-lives under a WKB approximation, which is emphasized in this work. The results show that the shell effects play a significant role in the estimation of the α decay half-lives within the actinide region.Predictions of the α decay half-lives are then generated for superheavy nuclei, which will provide useful information for future experiments.     

Fine structure of the okα X-ray emission band in Sc3+-activated lithium-manganese ferrites

The ok x-ray emission band of oxygen in a group of magnetically soft lithium squareloop ferrites has been obtained for the first time. The form of this band is complicated, by number and position it is similar to the FeK₅ band in the same ferrites, which suggests that the 3d states of Fe are significantly hybridized with the 2p states of oxygen and that the latter could participate in Anderson indirect exchange. The effect of small additions of Sc ions, improving the properties of the ferrite, on the spectrum of the ferrite is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 53–56, November, 1987.     

Fine structure of the emission spectrum of a two-dimensional electron–hole liquid in SiGe/Si quantum wells

The fine structure of the emission spectrum of a quasi-two-dimensional electron–hole liquid in shallow SiGe/Si quantum wells is observed experimentally. This fine structure is explained by the occurrence of steps in the density of states resulting from the coexistence of light and heavy holes in the liquid phase and by the interaction of charge carriers with charge-density oscillations in the liquid.     

Crystallographic aspects of structure formation under the β → α transformation in oriented cobalt single crystals

The crystallographic parameters of the β → α transformation in oriented cobalt single crystals quenched from 1000°C have been studied by X-ray structure analysis and light microscopy. It is shown that the orientation of martensite crystals of the α phase correspond to the Wasserman orientation relationship.     

Calculation of α decay half-lives for superheavy elements using the double folding model＊

α decay half-lives of some new synthesized superheavy elements, possibly synthesized superheavy elements and decay products are calculated theoretically within the WKB approximation by using microscopic α-nucleus interaction potentials. These nuclear potentials between the α particle and daughter nuclei are obtained by using the double folding integral of the matter density distribution of the α particle and daughter nuclei with a density-dependent effective nucleon-nucleon interaction, in which the zero-range exchange term is supplemented. The calculated α decay half-lives are compared with those of the different models and experimental data. It is shown that the present calculation successfully provides the half-lives of the observed decays for some new superheavy elements and therefore gives reliable predictions for α decay of possibly synthesized superheavy elements in future experiments.     

Possible α decay chains from isotopes of superheavy element 120

We investigate the α decay half-lives of even-Z superheavy nuclei up to Z = 120 by the modified two-potential approach. Based on the density-dependent cluster model, the α daughter potential is obtained from the double folding integral, taking into account the effect of nuclear deformation. A reasonable formula related with the fissility parameter and the fission barrier height, is applied to evaluate the spontaneous fission half-lives of the studied nuclei. After the performance of the competition between α decay and spontaneous fission, possible α decay chains are proposed in pursuit of being useful for the future experiment.     

Geometry of the effective Majorana neutrino mass in the 0νββ decay

The neutrinoless double-beta (0νββ) decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass <m>_ee. We put forward a novel ‘coupling-rod’ diagram to describe <m>_ee in the complex plane, by which the effects of the neutrino mass ordering and CP-violating phases on <m>_ee are intuitively understood. We show that this geometric language allows us to easily obtain the maximum and minimum of |<m>_ee|. It remains usable even if there is a kind of new physics contributing to <m>_ee, and it can also be extended to describe the effective Majorana masses <m>_eμ, <m>_eτ, <m>_μμ, <m>_μτ and <m>_ττ which may appear in some other lepton-number violating processes.