Creation of localized optical waves that Do not obey the radiation condition at infinity

X-ray bursts have been suggested as a possible site for the astrophysical rp-process. The time scale for the process is governed by beta-decay half-lives of several even-even N = Z waiting point nuclei, in particular, N = Z = 40 80Zr. A 4.1(+0.8/-0.6)-s beta(+)/EC half-life for 80Zr was determined by observing delayed 84-keV gamma rays depopulating a T(1/2) = 4-&mgr;s isomer at 312 keV in the daughter 80Y. As this half-life is lower than many previously predicted values, the calculated excessive production of A = 80 nuclides in astrophysical x-ray burst scenarios is reduced, and less extreme conditions are necessary for the production of heavier nuclides.     

Natural radioactivity of paleozoic and mesozoic sedimentary rocks from the Upper Silesian Coal Basin borders (Poland) — <Emphasis Type="Italic">in situ</Emphasis> gamma ray measurements

Sedimentary rocks from the borders of the Upper Silesian Coal Basin are the most popular origin of building materials in whole Silesia region. In situ gamma ray spectrometry was used to determine the activity concentration of nuclides from U series, Th series and potassium ⁴⁰K in almost every kind of sedimentary rocks outcropping in the studied region. Measured activity concentration of particular nuclides such as ⁴⁰K, U series, and Th series are mostly not higher than average activity concentrations of these nuclides in the continental crust. However, there are some significant exceptions such as clays from Blanowice and Krasiejow. In spite of that there isn’t any reason to stop using these rocks as building or other industrial material sources.     

Semi-gross theory of nuclear β-decay

The gross theory of β-decay is refined to take into account shell effects of the parent nuclei, and the resulting theory is named semi-gross theory. In this theory, the one-particle energy distribution in the parent nucleus is taken to have structures, and the one-particle strength function is assumed to depend on the quantum numbers of the initial state of the decaying nucleon. β-decay (partial) half-lives are calculated for 1659 nuclides, and the results are compared with experimental data as well as with those calculated by the gross theory. The β-decay strength functions are shown for two selected nuclides, and briefly discussed. These numerical studies confirm that the semi-gross theory includes some part of the shell effects correctly, although there still remain deviations of the theoretical results from experimental data, which should, at least partly, be due to shell effects of the daughter nuclei. Comparison of the present results with microscopic theories shows that the overall accuracy of the semi-gross theory is comparable with those of the microscopic theories.     

Natural radioactivity of paleozoic and mesozoic sedimentary rocks from the Upper Silesian Coal Basin borders (Poland) — in situ gamma ray measurements

Sedimentary rocks from the borders of the Upper Silesian Coal Basin are the most popular origin of building materials in whole Silesia region. In situ gamma ray spectrometry was used to determine the activity concentration of nuclides from U series, Th series and potassium ⁴⁰K in almost every kind of sedimentary rocks outcropping in the studied region. Measured activity concentration of particular nuclides such as ⁴⁰K, U series, and Th series are mostly not higher than average activity concentrations of these nuclides in the continental crust. However, there are some significant exceptions such as clays from Blanowice and Krasiejow. In spite of that there isn’t any reason to stop using these rocks as building or other industrial material sources.     

Schaleneffekt und α-Halbwertszeit

For the prediction of half-lives for α-decay a semiempirical equation is given. Taking into account a mean excitation energy of the daughter nuclei the constants in the equation for the α-half-lives were reevaluated using the latest published decay schemes. The ratios of experimental and calculated half-lives show a systematic behaviour if plotted versus the shell effects. Using this correlation the α-half-lives for unknown nuclides can be predicted with an improved accuracy.     

Independent Yield Measurement for the Hg-Isotope Products From 600 MeV 18O+natPb(thick target) System (Ⅰ) Experiment and Technique

With an on-line, gas-thermochromatographic Hg element separation as well as a special detection technique, the independent cross sections of the radioactive Hg-isotopes produced from a 600MeV ¹⁸O +^natPb(thick target) reaction system were determined. The independent cross sections of 22 Hg-isotope nuclides in the mass range from ¹⁸⁰Hg to ²⁰⁹Hg were measured. The experimental set-up, the detection technique, the γ-spectrum analyses and the extraction method of production cross sections based on the γ activities from the successively decaying daughter nuclei were described.     

Development and production of <Superscript>81</Superscript>Rb/<Superscript>81m</Superscript>Kr radionuclide generator in NPI

A project of ⁸¹Rb production and ⁸¹Rb/^81mKr generator manufacturing is described. ⁸¹Rb nuclide is produced on U-120M cyclotron via Kr(p, 2n)Rb reaction using pressurised gaseous target. Generator of a “dry” type is based on the sorption of ⁸¹Rb on an ion-exchange paper from which the daughter ^81mKr is eluted by air. Parameters of targetry and generator assembly are given. Generator which will be manufactured under pharmaceutical “clean” conditions is intended for lung ventilation studies in nuclear medicine.     

COMPLIS experiments: COllaboration for spectroscopy Measurements using a Pulsed Laser Ion Source

Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Q_s and changes of the nuclear mean square charge radius δ〈r_c ²〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

New superheavy element isotopes: ²⁴²Pu(⁴⁸Ca,5n) ²⁸⁵114

The new, neutron-deficient, superheavy element isotope 2??114 was produced in ??Ca irradiations of 2?2Pu targets at a center-of-target beam energy of 256 MeV (E*=50 MeV). The α decay of 2??114was followed by the sequential α decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269Sg. 265Rf was observed to decay by spontaneous fission. The measured α-decay Q values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The2?2Pu (??Ca,5n2)2??114 cross section was 0.6(-0.5)+0.9 pb.     

Accelerated alpha-decay of uranium isotopes induced by exposure of aqueous solution of uranium salt with gold nanoparticles to laser radiation

Laser-induced accelerated alpha-decay of ²³²U nuclei under laser exposure of Au nanoparticles in aqueous solutions of uranium salt has been experimentally studied. It is demonstrated that the decrease in the alpha-activity depends strongly on the peak intensity of laser radiation in the liquid and reaches a maximum at 10¹²–10¹³Wcm^?2. The decrease in the alpha-activity of the exposed solutions is accompanied by deviation of gamma-activities of daughter nuclides of ²³²U from their equilibrium values. Experimental data on the accelerated alpha-decay of ²³⁸U under similar experimental conditions are also presented. Possible mechanisms of laser effect on the alpha-activity are discussed in terms of the amplification of the electric field of laser wave on metallic nanoparticles.     

Direct mass measurements on the superallowed emitter 74Rb and its daughter 74Kr: isospin-symmetry-breaking correction for standard-model tests

The decay energy of the superallowed beta decay 74Rb(beta+)74Kr was determined by direct Penning trap mass measurements on both the mother and the daughter nuclide using the time-of-flight resonance technique and was found to be Q=10 416.8(4.5) keV. The exotic nuclide 74Rb, with a half-life of only 65 ms, is the shortest-lived nuclide on which a high-precision mass measurement in a Penning trap has been carried out. Together with existing data for the partial half-life as well as theoretical corrections, the decay energy yields a comparative half-life of Ft=3084(15) s for this decay, in agreement with the mean value for the series of the lighter nuclides from 10C to 54Co. Assuming conserved vector current, this result allows for an experimental determination of the isospin-symmetry-breaking correction deltaC.     

The effect of nonlinearity in relativistic nucleon–nucleon potential

A simple form for nucleon–nucleon (NN) potential is introduced as an alternative to the popular M3Y form using the relativistic mean field theory (RMFT) with the non-linear terms in σ-meson for the first time. In contrast to the M3Y form, the new interaction becomes exactly zero at a finite distance and the expressions are analogous with the M3Y terms. Further, its applicability is examined by the study of proton and cluster radioactivity by folding it with the RMFT-densities of the cluster and daughter nuclei to obtain the optical potential in the region of proton-rich nuclides just above the double magic core¹⁰⁰Sn. The results obtained were found comparable with the widely used M3Y NN interactions.     

Optimal reactions for synthesis of nuclides of element 108

The cross sections for the production of nuclides of element 108 via hot fusion evaporation reactions are studied using a two-parameter Smoluchowski equation. The optimal reactions for the synthesis of new nuclides of element 108 with mass numbers from 266 to 271 are suggested. The macroscopic-microscopic approach predicts a strong deformed shell closure at Z \approx 108 and N=162. The synthesis of more nuclides of element 108 is meaningful to the confirmation of the existence of this deformed shell closure.     

基于HIRFL-CSR测量丰中子重核质量的建议

丰中子重核区有大量原子核质量未知,迫切需要实验测量。我们建议,利用兰州重离子加速器研究装置HIRFL-CSR上的等时性质谱术,高精度测量204Pt等丰中子重核的质量。CSR质量测量实验中,在目标核产额尽可能高的前提下,需要每次注入都有多个离子同时储存到实验环CSRe中,才能针对逐次注入修正磁场晃动的影响,得到高精度测量结果。但在丰中子核区,当目标核产生截面非常低时,每次注入能储存到环中的离子数目太少。为了解决这个问题,我们提出了一种"混合厚度靶"的方法,在不明显改变目标核产额的情况下,显著增加同时储存在CSRe中的离子数,满足实验要求。模拟计算表明,在CSRe测量丰中子重核质量是可行的,并推荐了实验的设置。     

The fermion dynamic symmetry model and superdeformation near A = 220

The FDSM prediction of oblate superdeformed minima in nuclides with 84<Z<90 and 124<N<130 is studied with a Strutinsky method calculation of energy surfaces. Oblate superdeformed minima are found for slightly heavier nuclides. A critique of the application of the FDSM in the heavy elements is presented. Prolate superdeformation near A = 220 is re-examined.     

北航沙河校区土壤中40 K、238 U、232 Th相对含量的实验测量

环境中天然伽马射线主要来源于⁴⁰K以及钍系、铀系和锕系.通过探测伽马射线来识别放射性核素并得到它们的相对含量,是核科学与核技术中的一个重要方法.利用高分辨的高纯锗探测器,北航以及国内部分高校已开设了鉴别环境中放射性核素的实验.在此基础上,本文进一步利用特征γ射线与递次衰变规律,对北航沙河校区土壤中的⁴⁰K、²³⁸U和²³²Th的相对含量进行了测量,结果与普查数据一致.     

A new alpha-particle-emitting isotope 259Db

An isotope of the element 105 with mass number 259 has been produced via the reaction ²⁴¹Am(²²Ne, 4n)²⁵⁹Db at E _lab = 118 MeV. The reaction products were transported and collected using the helium-jet technique and the rotating wheel apparatus. The α-decays of the products and their daughter nuclides were detected by a set of Si(Au) detectors arranged ingeniously. The Z and A of the nuclide have been unambiguously identified by the genetic relationship between the new activity and the known nuclide ²⁵⁵Lr established by α-recoiled milking measurement. The new nuclide ²⁵⁹Db has a half-life of 0.51±0.16 s and decays by alpha-particle emission of E _α = 9.47 MeV. Furthermore, the nuclide ²⁵⁸Db and its daughter ²⁵⁴Lr have also been clearly observed using the same projectile-target combination. Their half-lives and α-particle energies determined in this work are in agreement with previous known data, thus also proving the reliability of our assignment of ²⁵⁹Db. Received: 7 December 2000 / Accepted: 6 February 2001     

Kr2+辐照导致的Ca8LnNa(PO4)6F2(Ln=La,Nd和Sm)磷灰石结构陶瓷材料的非晶转变

采用传统固相烧结法成功制备出磷灰石结构材料Ca₈LnNa（PO₄）₆F₂（Ln=La,Nd和Sm）,并通过常规X射线衍射（X-ray diffraction,XRD）进行表征确定三种样品都为单一相。在室温条件下用800 keVKr2+对三种样品进行辐照实验,辐照后的样品利用掠入射X射线衍射（grazing incidence X-ray diffraction,GIXRD）进行表征获取其表面辐照损伤层的结构信息。发现在实验辐照剂量范围内（1.0×1014~7.0×1014cm-2）三种样品都发生了从晶体结构到非晶结构的转变,不过三种样品的抗辐照非晶性能却有差异,抗辐照非晶能力大小关系是Ca₈LaNa（PO₄）₆F₂ > Ca₈NdNa（PO₄）₆F₂ > Ca₈SmNa（PO₄）₆F₂。这是由于在Ca₈LnNa（PO₄）₆F₂中,当镧系核素半径越小时,将有更大概率占据Ca（2）位置与F形成比Ca-F更弱的离子键。因此,镧系核素半径越小,辐照下将有更多的点缺陷保留下来,更容易发生非晶相变。     

Penning trap mass spectrometry for nuclear structure studies

High-precision mass measurements as performed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN are an important contribution to the investigation of nuclear structure. Precise nuclear masses with less than 0.1 ppm relative mass uncertainty allow stringent tests of mass models and formulae that are used to predict mass values of nuclides far from the valley of stability. Furthermore, an investigation of nuclear structure effects like shell or sub-shell closures, deformations, and halos is possible. In addition to a sophisticated experimental setup for precise mass measurements, a radioactive ion-beam facility that delivers a large variety of short-lived nuclides with sufficient yield is required. An overview of the results from the mass spectrometer ISOLTRAP is given and its limits and possibilities are described.      

Measurement of radon and thoron concentration by using LR-115 type-II plastic track detectors in the environ of Brahmaputra Valley, Assam, India

Radon/thoron and their progeny concentrations were measured in different types of dwellings at different locations around industrial areas, cities and rural areas of Brahmaputra Valley of Assam by using LR-115 (type-II) plastic detector. Radon levels of different dwellings were analysed with reference to the nature of building materials, ventilation patterns and the types of underlying soil. The results were discussed under the light of exposure limits set by ICRP. The average concentrations of indoor radon and thoron varied from 39.5 to 215.2 Bqm⁻³ and 12.9 to 37.6 Bqm⁻³, respectively. The estimated inhalation dose due to radon, thoron and their daughter products in the study areas varied from 0.53 to 1.00 μSvh⁻¹.