Search for beta-delayed fission of Ac-228

Radium was radiochemically separated from natural thorium. Thin Ra-228 ->beta Ac-228 sources were prepared and exposed to mica fission track detectors, and measured by an HPGe gamma-ray detector. The beta-delayed fission events of Ac-228 were observed and its beta-delayed fission probability was found to be (5 +/- 2)x10(-12).

Observation of a pi h(9/2) circle times nu i(13/2) oblate band in Tl-188

Excited states in Tl-188 have been studied experimentally using the Gd-157(Cl-35;4n) reaction at a beam energy of 170 MeV. A rotational band built on the pi h(9/2) x nu i(13/2) configuration with oblate deformation has been established for Tl-188. Based on the structure systematics of the oblate pi h(9/2) x nu i(13/2) bands in the heavier odd-odd Tl nuclei, we have tentatively proposed spin values for the new band in Tl-188. The pi h(9/2) x nu i(13/2) oblate band in Tl-188 shows low-spin signature inversion, and it can be interpreted qualitatively by the two-quasiparticle plus rotor model including a J-dependent p-n residual interaction.

Properties of the pi h(9/2)circle times nu i(13/2) oblate band in Tl-188

High spin states in Tl-188 have been investigated via the Gd-157(Cl-35,4n) reaction at beam energy of 170 MeV. A rotational band built on the pi h(9/2) circle times nu(13/2) configuration with oblate deformation has been established. Considering the similarity between the band structure observed in odd-odd Tl nuclei, spin values have been tentatively proposed for the new band in Tl-188. The pi h(9/2) circle times nu(13/2) oblate band in Tl-188 shows low-spin signature inversion, and it can be interpreted qualitatively by the two quasiparticle plus rotor model including a J-dependent p-n residual interaction.

beta-delayed proton decays of Tb-140 and Dy-140 as well as the spin and parity of Dy-143

Tb-140 and Dy-141 were produced via fusion evaporation in the reaction Ca-40+Cd-106. Their beta-delayed proton decays were studied by means of "p-gamma" coincidence in combination with a He-jet tape transport system, including half-lives, proton energy spectra, gamma-transitions following the proton emissions, and the branching ratios to the low-lying states in the grand-daughter nuclei. The ground-state spins and parities of Tb-140 and Dy-141 were extracted as 7(+/-) and 9/2(+/-), respectively, by fitting the experimental data with a statistical model calculation. The configuration-constrained nuclear potential energy surfaces (NPES) of Tb-140 and Dy-141 were calculated by using the Woods-Saxon Strutinsky method, which indicate the ground-state spins and parities of Tb-140 and Dy-147 to be 7(+) and 9/2(-), respectively. In addition, the configuration-constrained NPES of Dy-143 was also calculated by using the same method. From the NPES a 1/2(+) ground state and a 11/2(-) isomer with the excitation energy of 198keV were found. The calculated results are consistent with our experimental data on the decay of Dy-143 reported in Eur. Phys. J., 2003, A16: 347-351.

beta(+)/EC-decay study of Ir-176 neutron-deficient isotope

The beta(+)/EC decay of doubly odd Ir-176 has been investigated using Nd-146(Cl-35, 5n gamma)Ir-176 heavy ion fusion evaporation reaction at 210MeV bombarding energy. With the aid of a helium-jet recoil fast tape transport system, the reaction products were transported to a low-background location for measurements. Based on the data analysis, the previously published gamma rays in Ir-176 decay were proved, moreover, 3 new levels and 10 new gamma rays were assigned to Ir-176 decay. The new level scheme of Os-176 with low excitation energy has been established. The time spectra of typical gamma rays clearly indicate a long-lived low-spin isomer in Ir-176 nuclide.

Study of quasiparticles bands in odd-odd Au-188

High-spin level structure of Au-188 has been studied via the Yb-173(F-19, 4n gamma) reaction using techniques of in-beam gamma-ray spectroscopy. Based on the experimental results, the level scheme of 188Au has been revised significantly. The previously reported positive parity levels have been modified and a new 20(+) level was proposed to feed the 18(+) states via two low-energy transitions. The existence of the 20(+) and the level structures above it are similar to those in the neighboring odd-odd Au-190,Au-192, therefore, the pi h(11/12)(-1)circle times-vi(13/2)(-2)h(9/2)(-1) configuration was assigned to the 20(+) state.

Raman investigation of ion-implanted ZnO films

ZnO thin films were implanted at room temperature with 80 keV N+ or 400 keV Xe+ ions. The implantation fluences of N+ and Xe+ ranged from 5.0 x 10(14) to 1.0 x 10(17)/cm(2), and from 2.0 x 10(14) to 5.0 x 10(15)/cm(2), respectively. The samples were analyzed using Raman spectroscopy and the Raman scattering modes of the N- and Xe-ion implanted samples varying with implantation fluences were investigated. It was found that Raman peaks (bands) at 130 and 578 cm(-1) appeared in the spectra of ion-implanted ZnO samples, which are independent of the ion species, whereas a new peak at 274 cm(-1) was found only in N-ion implanted samples, and Raman band at 470 cm(-1) was found clearly in Xe-ion implanted samples. The relative intensity (peak area) increased with the increasing of the implantation fluences. From the comparison of the Raman spectra of N- and Xe-ion implanted ZnO samples and considering the damage induced by the ions, we analyzed the origin of the observed new Raman peaks (bands) and discussed the structure changes of ZnO films induced by N- and Xe-ion implantations.

High-spin states in Au-188: Further evidence for nonaxial shape

The high-spin level structure of Au-188 has been investigated via the Yb-173(F-19,4n gamma) reaction at beam energies of 86 and 90 MeV. The previously reported level scheme has been modified and extended significantly. A new I-pi = 20(+) state associated with pi h(11/2)(-1) circle times nu i(13/2)(-2)h(9/2)(-1) configuration and two new rotational bands, one of which is built on the pi h(9/2) circle times nu i(13/2) configuration, have been identified. The prolate-to-oblate shape transition through triaxial shape has been proposed to occur around Au-188 for the pi h(9/2) circle times nu i(13/2) bands in odd-odd Au isotopes. Evidence for pi h(11/2)(-1) circle times nu i(13/2)(-1) structure of nonaxial shape with gamma < -70 degrees has been obtained by comparison with total Routhian surface and cranked-shell-model calculations.

Nucleon form factors in a light-cone quark model with two-photon exchange

We estimate the two-photon exchange corrections to both proton and neutron electromagnetic physical observables in a relativistic light cone quark model At a fixed Q(2) the corrections are found to be small in magnitudes. but strongly dependent oil scattering angle Our results are comparable to those obtained from simple hadronic model in the medium momentum transfer region (C) 2009 Elsevier B V All rights reserved

Long-distant contribution and chi(c1) radiative decays to light vector meson

The discrepancy between the PQCD calculation and the CLEO data for chi (c1)->gamma V (V=rho (0), omega, phi) stimulates our interest in exploring other mechanisms of chi (c1) decay. In this work, we apply an important non-perturbative QCD effect, i.e., the hadronic loop mechanism, to study chi (c1)->gamma V radiative decay. Our numerical result shows that the theoretical results including the hadronic loop contribution and the PQCD calculation of chi (c1)->gamma V are consistent with the corresponding CLEO data of chi (c1)->gamma V. We expect further experimental measurement of chi (c1)->gamma V, which will be helpful to test the hadronic loop effect on chi (c1) decay.

Band properties of the transitional nucleus Pt-189

High-spin states in Pt-189 have been studied with the in-beam gamma-spectroscopy method via the Yb-176(O-18, 5n) reaction at beam energies of 88 MeV and 95 MeV. A new level scheme of Pt-189 has been established. Rotational bands based on the upsilon i(13/2)(-1), upsilon f(5/2)(p(3/2)) and upsilon i(13/2)(-2)upsilon f(p(3/2)) configurations, as well as several structures with irregular level spacings, have been observed. Properties of rotational bands have been analyzed in the framework of triaxial particle-rotor model. A gamma similar to -30 degrees triaxial shape and a near prolate shape have been proposed to the upsilon i(13/2)(-1) and uf(5/2)(p(3/2)) bands, respectively. Two Delta I=2 transition sequences with similar energies have been observed, and they have been proposed to be associated with the upsilon i(13/2)(-1)upsilon f(5/2)(p(3/2)) configuration. According to the relevant Nilsson orbitals, the bands built on the upsilon i(13/2)(-1)upsilon f(5/2)(p(3/2)) configuration could be interpreted as a pair of pseudo-spin partner.

激光离子源用于A>170重丰中子新核素的研究

本文概述了 A > 170 质量区重丰中子同位素研究的主要工作和意义；介绍了 A > 170 重丰中子同位素合成、分离和鉴别方法；详细论述了激光离子源的原理、设计及其同传统离子源相比所具有的优越性；在文章结尾，设计了一个物理实验，实验目的在于：1）寻找 ~(181)Yb新核素；2）揭示天体物理学中~(180m)Ta 的产生问题。我们对反应截面进行了分析，并对产额进行了估计，证明了此实验设计的合理性，进而说明了带激光离子源的同位素分离器适用于产生截面很低的新核素和衰变研究。本文重点讨论了激光离子源的各方面问题：介绍了激光多步共振电离原理和激光离子源原理；具体分析了热毛细管式激光离子源元素选择性的产生及其影响的因素；讨论了在设计、加工过程中的具体问题；描述了所使用的激光技术；通过在线实验验证了热毛细管式激光离子源的元素选择性和分离效率。

球形核139Ce和过渡区核189Pt高自旋态能级结构研究

本论文主要包括以下两部分： 利用能量为50 MeV的 12 C 束流，通过反应 130 Te( 12 C,3n)产生了 139 Ce 的高自旋态。 基于标准在束核谱学实验方法，利用由14套BGO（AC）HPGe 探测器组成的探测器阵 列，进行了X- γ -t和 γ - γ -t符合测量，更新并扩展了 139 Ce 的高自旋能级纲图。139 Ce 的能级结构具有球形原子核的典型特征，其高自旋态是由单粒子激发形成的。本文利用 经验壳模型计算了 139 Ce 的多准粒子激发态能量，研究了其高自旋激发态的多准粒子特 性。 利用能量为88和95 MeV的 18 O 束流，通过重离子熔合蒸发反应 176 Yb( 18 O,5n)，布 居了 189 Pt 的高自旋激发态。实验采用 GEMINI γ射线探测器阵列，进行了X- γ -t 和 γ - γ -t 符合测量。基于γ - γ符合关系、γ射线相对强度、强度平衡原理和交叉跃迁等 信息，建立了新的 189 Pt 高自旋态能级纲图。实验观测到基于 1 13/2 i υ − ， 5/23/2 () f p υ 和 2 13/25/23/2 () ifp υυ − 组态的转动带以及多准粒子激发能级。其中， 1 13/2 i υ − 带的优惠和非优惠旋 称分支分别被扩展到 49/2+ 和31/2+ 能级。本工作利用三轴粒子-转子模型分析了基于 1 13/2 i υ − ， 5/23/2 () f p υ 组态的转动带性质，分析了它们波函数的主要成分，并建议它们分别 具有三轴形变和长椭形变。实验上发现结构非常相近的两个能级序列，我们建议它们具 有 2 13/25/23/2 () ifp υυ − 组态。第一次利用粒子-转子模型计算了这个基于三准粒子组态的转动 带能级能量，很好地再现了实验结果，并建议此带具有扁椭形变。由于与这个组态相应 的 Nilsson 轨道量子数显示了赝自旋量子数特征，我们建议此三准粒子组态转动带为赝 自旋伙伴带。

奇奇核166,168Lu和奇中子核87Zr高自旋态的实验研究

本论文主要进行了奇奇核~(166)Lu、~(168)Lu和奇中子核~(87)Zr的高自旋态的研究工作，对它们高自旋态的一些物理现象进行了讨论。并且首次对1／2~-[541](direct X)vi_(13/2)组态带的系统学规律进行了总结。主要由以下三个部分组成：~(166,168)Lu高自旋态的研究在最近有关形变奇奇核高自旋态的研究工作中，随着实验上π1／2-[541](direct X)vi_(13/2)带自旋的确定，人们发现除了130区的兀h_(11/2)(direct X)vh_(11/2)和160区的兀h_(11/2)(direct X)vi_(13/2)组态带低自旋旋称反转以外，π1／2~-[541](direct X)vi_(13/2)带的低自旋也是反转的，该转动带低自旋旋称反转现象引起了人们的很大的兴趣并得到很广泛的研究，为了通过π1／2~-[541](direct X)vi_(13/2)带与已知自旋和宇称的基态和一些低激发态相连，确定该转动带的自旋，人们付出了很大的努力。特别是最近几年，一些实验上自旋的确定，使得研究π1／2~-[541](direct X)vi_(13/2)组态带低自旋旋称反转的系统学规律成为可能。需要指出的是在以前的研究结果中，~(166)Lu的π1／2~-[541](direct X)vi_(13/2)组态带的能级摆动规律与相邻奇奇核该组态带的能级摆动规律严重不符，澄清该疑点是我们重新研究该核的主要动力之一。在以前~(168)Lu的研究工作中，只在~(168)Lu中发现两个带，但其中只有晕带的组态得到指定，根据带结构和旋称劈裂的大小估计另一个带极有可能是π1／2~-[541](direct X)vi_(13/2)带。为了澄清以上这些疑点和得到π1／2~-[541](direct X)vi_(13/2)组态带的系统学规律，我们重新研究了。~(166,168)Lu的高自旋态。另外(h_(11/2)_p(i_(13/2))_n组．态带的低自旋旋称反转是一个广为人知的物理现象，但在以前的有关~(166）Lu的结果中对(h_(11/2))_p(i_(13/2))_n组态带白旋的确定与该组态带低自旋旋称反转系统规律相反，这也是我们对~(166)Lu重新研究的一个原因。实验是在北京中国原子能科学研究院HI-13串列加速器上进行的，分别利用入射能量为97MeV和92MeV的~(19)F束通过熔合蒸发反应~(152)Sm(~(19)F,~5n)~(166)Lu和~(154)Sm(~(19)F5n)~(168)Lu布居了~(166)Lu和~(168)Lu的高自旋态。用十台HpGe探测器组成的探测阵列进行γ-γ符合测量，对~(166)Lu和~(168)Lu分别记录了约1.27 * 10~8和0.25 * 10~8个两重和两重以上的符合事件。在~(166)Lu中，共发现了五条转动带，根据它们的顺排在0.28MeV均没有出现上弯，意味着它们的中子均占居i_(13/2)轨道，同时根据在~(165)Lu和~(167)Lu只发现基于9／2~-[514]、7／2~-[404]、1／2~-[541]、1／2~+[411]和5／2~+[402]轨道的转动带及在~(165)Yb和~(167)Hf中晕带均为5／2~+[642]的事实，那么由上述质子轨道和中子轨道组成的转动带是本文发现的五条带的最可能的侯选者。本实验中观察到的五条转动带分别基于7／2~+[404](direct X)5／2~+[642]、9／2~-[514](direct X)5／2~+[642]、1／2~-[541](direct X)5／2~+[642]、5／2~+[402](direct X)5／2~+[642]和1／2~+[642](direct X)5／2~+[642]轨道的转动带。和以前的数据相比主要有以下几点改进：(A)在以前的结果中，包括2000年新发表的有关~(166)Lu的文章，他们均把本文~(166)Lu纲图中(5)和(6)退激系列归属于π1／2~-[541](direct X)v5／2~+[642]转动带，而在本文中通过符合关系一个新的退激系列(7)被发现，根据(6)和(7)之间的符合关系、带交叉频率、γ射线强度和B(M1)／B(E2)的比值等关系，本文认为新发现的退激系列(7)与(6)组成新的π1／2~-[541](direct X)v5／2~+[642]转动带.以前的结果的错误在于把属于1／2~-[541](direct X)5／2~+[642]转动带的α = 0与1／2~-[541](direct X)5／2~+[642]转动带的α = 0误归于一个带，这就澄清了原文献中π1／2~-[541](direct X)v5／2~+[642]转动带能级摆动规律与相邻奇奇核该组态带能级摆动规律不符的疑点，同时把原文献中误归于π1／2~-[541](direct X)v5／2~+[642]转动带的那一个退激系列(5)重新指定为1／2~+[411](direct X)5／2~+[642]带(α = 0)；(B)通过分析实验数据、跃迁能量系统学和运用顺排相加性规则对以前实验中建立的9／2~-[514](direct X)5／2~+[642]和7／2~+[404](direct X)5／2~+[642]带的自旋进行了重新指定，把它们的自旋在原文的基础上加1个单位，澄清了以前的有关~(166)Lu结果中对9／2~-[514](direct X)5／2~+[642]组态带自旋的确定与该组态带低自旋旋称反转事实相反的疑点；(C)新发现了基于9／2~-[541](direct X)5／2~+[642]组态的转动带。在~(168)Lu中，共观察到了四条转动带，分别是π1／2~-[541](direct X)v5／2~+[642]、7／2~+[404](direct X)5／2~+[642]、 9／2~-[514](direct X)5／2~+[642]和7／2~+[404](direct X)5/2~-[523](本文新建立的带)带，本文对其中晕带7／2~+[404](direct X)5／2~+[642]的K值取值与原文献中的取值不同，并根据能量系统学和带头激发能指出不同的原因。 除以上所述外，本文还给出了~(166)Lu和~(168)Lu各γ射线的强度、转动参数A、较强γ射线的DCO值、分支比和B(M1)／B(E2)等实验值。基于实验和理论预期的B(M1)／B(E2)比值的比较、各带带交叉行为、顺排相加性、带头激发能和转动参数A对各带的组态和自旋进行了指定。最后通过对实验上对~(162,164)Tm、~(174)Ta和~(176)Re的π1／2~-[541](direct X)vi_(13/2)组态带p-n剩余相互作用信息的提取，指出奇质子核中1／2~-[541]带的带交叉频率相对相邻偶偶核的延迟约三分之一到一半左右，其原因是由于p-n剩余相互作用所造成的(包含了对效应和形变变化的CSM模型能够解释另一半的偏离)，可以定性的认为正是由于形变、对相互作用的变化和剩余p-n相互作用三者相结合导致了整个的1／2~-[541]带中带交叉频率的偏离。旋称反转机制综述和πh_(932)(direct X)vi_(l3/2)组态的系统学首先对导致旋称反转的各种机制做一简单回顾，同时对ππh,u2⑩vi,钔组态带系统学规律做一简单总结，总结了πh_(11/2)(direct X)Vi_(13/2)组态带的跃迁能量系统学规律。在最近，随着~(162)Tm、~(164)Tm、~(174)Ta和~(176)Re等几个奇奇核中半退耦带1／2~-[541](direct X)vi_(13/2)的自旋通过实验方法的确定，人们惊奇的发现在上述这些核~(162)Tm、~(164)Tm、~(174)Ta和~(176)Re)中半退耦带1／2~-[541](direct X)vi_(13/2)在低自旋区都是旋称反转的。人们就会很自然的回头去看那些在该区已经布居1／2~-[541](direct X)vi_(l3／2)组态带的那些核，结果发现对于该组态带的自旋的指定是很杂乱无章的，有些自旋的确定即不符合能量系统学又与顺排相加性规则相悖，如在~(172)Ta和~(178)Re中(值得指出的是有关这两个核的文章均是在十年前发表的)，自旋的指定明显与最近发表的该区πhg_(9/2)(direct X)vi_(13/2)组态带自旋不符，本文通过能量系统学和顺排相加性对~(172)Ta和~(178)Re的1／2~-541](direct X)vi_(13/2)组态带自旋做了修改，分别增加了3h和h。本文通过对最新结果~(162)Tm、~(164)Tm、~(170)Lu、~(170,174,176)Ta、~(176)Re、~(180)Ir)和以前的结果(~(172)Ta和~(178)Re)及本文的结果(~(166,168)Lu)对上述12个核的1／2~-[541](direct X)vi_(13/2)组态带的S(I) = E(I)-E(I-1)- E(I + 2)-E(I + 1)-E(I - 1)-E(I - 2)]／2～I的变化图的分析，继A ≈ 130区7πh_(11/2)(direct X)vh_(11/2)组态带和A ≈ 160区πh_(11/2)(direct X)vi_(13/2)组态带的系统学规律以后，首次总结出A ≈ 170区π1／2~-541](direct X)vi_(13/2)组态带的系统学规律：反转点的自旋随N的增加而增加，随Z的增加而减小，与πh_(11/2)(direct X)和πh_(11/2)(direct X)vi_(13/2)转动带的系统学规律很相似，即反转点自旋均随中子和质子单调地变化。通过对各种理论模型的研究发现三轴形变、科里奥利力、带交叉与自反转和p-n相互作用在奇奇核中都有可能导致旋称反转，包含有p-n相互作用的粒子-转子模型在πh_(11/2)(direct X)和vh_(11/2)、πh_(11/2)和π1／2 ~-[541](direct X)vi_(13/2)组态带中的旋称反转上取得了某些成功，表明p-n相互作用在解释奇核低自旋反转现象中起着很重要的作用。通过对实验上π1／2~-[541](direct X)vi_(13/2)组态带旋称反转点与文献中理论计算值的比较，得出p-n相互作用强度的变化可能是导致π1／2~-[541](direct X)vi_(13/2)组态带症称反转点变化主要原因的结论。过渡区核~(87)Zr的高自旋态研究在A≈80区，许多原子核的中子和质子数都处在28和50两个满壳层之间，对于这些核而言，任何一种核子数的改变都有可能导致核形状的显著变化。有研究结果表明，对于40≤Z≤45的核来讲，N=46是变形核向球形核变化的转折点。在40≤N≤50区，对Zr(Z=40)同位素系列中诸原子核能级结构伴随中子数改变而发生的变化的研究将会帮助我们了解这个形状变化的过程。我们所研究的~(87)Zr含有47个中子，就处于这个过渡区。实验是在北京中国原子能科学研究院HI-13串列加速器上进行的，利用入射能量为118MeV的~(32)S束通过~(58)Co(~(32)S,3pn)~(87)Zr熔合蒸发反应布居。~（87）Zr的高自旋态，实验用的靶为附有Ta衬的厚度1082μg／cm~2的~(59)Co箔。用7台HpGe探测器组成的探测阵列进行γ-γ符合测量。同时采用一个小平面光子探测器探测低能γ射线。本实验记录了约1.5 * 10。个两重以上的符合事件，建立了自旋直到37／2和43／2的能级纲图。研究的结果表明：~(87)Zr与相邻同中子奇A核的正宇称低激发能级之间存在着很强的相似性，而与相邻奇A核同位素相比，结构变化明显， 这可能表明在该核区对核形变的影响中子占主要地位，质子影响较小。激发能随中子变化的比值图呈阶梯状，认为R ≈ 1.5，R_x ≈ 2.0和R_x ≥ 2.2分别代表核形变的三个区域，即球型核、过渡区核和形变核。通过与相邻(Z,N + 1)偶偶核低激发态能级相比较的方法对各低激发能级组态的主要成分进行了估计，发现随自旋的增加，出现了各能级组态之间的混杂。

磁控反应溅射制备钇掺杂TiO_2薄膜的研究

采用混合靶直流磁控反应溅射法,在玻璃基体上溅射沉积了含有氧化钇的TiO2薄膜。X-射线光电子能谱分析结果表明,薄膜是由Y2O3和TiO2复合氧化物组成的。钇的存在会抑制薄膜中二氧化钛晶体的形成。薄膜的紫外可见光谱透射率略有下降,而反射率有所增加。钇的掺杂对二氧化钛薄膜的光催化活性起负作用,光催化降解甲基橙反应的活性随钇含量的增加而下降。