Electromagnetic Transition Rates and Deformation Feature in 130Ce

Lifetimes of the excited states in light rare-earth nucleus ¹³⁰Ce have been measured using heavy ion reaction ¹¹⁶Sn(¹⁶O,2n)¹³⁰Ce at beam energy of 73MeV through analyzing the Doppler-broadened line shapes. The reduced transition probabilities B(E2) are extracted from these measurements. The experimental results show that the previously reported anomalously high B(E2) value has not been observed in the present work. The transition quadrupole moment for the yrast band varies with spin and corresponds to a triaxial deformation with γ≈7°.     

ISOMERIC CROSS SECTION RATIO IN THE 197Au(n,2n)196Au REACTION

Isomeric cross section ratio for the ¹⁹⁷Au (n, 2n) reaction at 15 MeV is measured by the activation method. Using the Huizenga and Vandenbosch method, the isomeric ratio is calculated for the reaction. From the comparison of the measured and theoretically calculated isomeric ratio, the values of the spin cut-off factor and nuclear moment of inertia are determined.     

Measurement of Some (n,2N) Reaction Cross Sections for Producing Long Half-Life Residues

Measurement of (n,2n) reaction cross sections for some nuclides,whose residues have long half-lives,is described.The activation method relative to the ⁹³Nb(n,2n)^92mNb reaction cross section was used.The cross sections of the ¹⁵¹Eu(n,2n)^150mEu、¹⁵³Eu(n,2n)¹⁵²Eu、¹⁵⁹Tb(n,2n)¹⁵⁸Tb and ¹⁰⁹Ag(n,2n)^108mAg reactions in the neutron energy range of 13.50—14.80MeV were measured.The neutron energies in this experiment were determined by means of the method of cross section ratios for ⁹⁰Zr(n,2n)^89m+gZr and ⁹³Nb(n,2n)^92mNb reactions.The results obtained were compared with other existing data.     

DETERMINATION OF THE AVERAGE NEUTRON ENERGY USING CROSS SECTION RATIO OF 58Ni(n,p)58m+gCo and 58Ni(n,2n)57Ni REACTIONS

The method of determination for average neutron energy from D-T reaction by using two silicon semiconductor detectors and the cross section ratios of ⁵⁸Ni(n,p)^58m+gCo and ⁵⁸Ni(n,2n)⁵⁷Ni reactions is described.The plot of the cross section ratio against the neutron energy has been obtained.The results have been compared with existing data.     

MEASUREMENT OF ISOMERIC CROSS-SECTION RATIO

The isomeric abolute cross-section and cross-section ratio have been measured by the direct activation method for the ⁴⁵Sc(n, 2n) ^44m,gSc reaction and 86Sr(n, 2n) ^85m,gSr reaction induced by 14.8+0.4 MeV neutrons. The experimental results are compared with the theoretical ones calculated by Huizenga-Vandenbosch theory and the spin cut-off parameter σ is determined.     

β-Delayed Proton Decay of 93Pd

The β-‘waiting point’nucleus ⁹³Pd has been produced via ⁵⁸Ni(⁴⁰Ca,3n2p) reaction. A helium-jet fast tape transport system was used in combination with p-γ coincidence measurement to identify the β-delayed proton precursor ⁹³ Pd, whose half-life has been measured to be 1.3±0.2s. The measured energy spectrum of β-delayed protons and relative branching ratios to the final states in the daughter nucleus ⁹²Ru are fitted by a revised statistic model calculation, and then the ground state spin of ⁹³Pd are assigned to be 9/2. Meanwhile, a nuclear energy-potential-surface (EPS) calculation is performed by using the Woods-Saxon Strutinsky method. The calculated result supports the ground state spin and parity of 9/2⁺ assignment.     

Extended Glauber Theory and Its Application in Halo Nucleus Scattering

We introduced an extended Glauber theory for a halo nucleus scattering, where the halo nucleons and the nuclear core were treated separately. Expressions of reaction and interaction cross sections of the halo nucleus scattering were derived. We took the halo structure of the projectile nucleus into account and adopted an improved optical limit approximation. In the framework of the extended Glauber theory, we studied the reaction cross section for the halo nucleus ¹⁴Be scattering on a target ¹²C. For comparison, the reaction cross sections of ¹²Be+¹²C were calculated as well. The density distribution of target ¹²C is taken from experiments, and those of the projectiles ¹²Be and ¹⁴Be were obtained by two methods. One is that the harmonic oscillator wave functions for ¹²Be and ¹⁴Be are used. The length of harmonic oscillator is adjusted to reproduce the reaction cross section of ¹²Be+¹²C at the high energy E=790MeV/u . The density distribution of ¹⁴Be was also calculated self-consistently in the relativistic mean field (RMF) theory, with a long tail wave functions for the two neutrons in ¹⁴Be. It was found that the calculated reaction cross sections for ¹²Be+¹²C at E=790MeV/u and E=56.5MeV/u were in good agreement with the experimental data no matter harmonic oscillator or RMF wave functions were used. In contrast, the experiments of the reaction cross sections for ¹⁴Be+ ¹²C could only be reproduced when the wave functions of two 2s_1/2 neutrons spreaded over with a long tail. It comes to a conclusion that two outside neutrons in ¹⁴Be form a halo structure.     

Measurement of Cross Sections for Pb(n,x)203Hg,W(n,x)182Ta and W(n,x)183Ta Reactions Induced by 14 MeV Neutrons

The cross sections for Pb(n,x)²⁰³Hg,W(n,x)^l82Ta and W(n,x)¹⁸³Ta reactions have been measured by the activation method. The neutron fluences were determined by the cross sections of ⁹³Nb (n,2n)^92mNb reaction. The neutron energies in the measurements were determined by the cross section ratios of Zr(n,2n)^89m+gZr and Nb(n,2n)^92mNb reactions.     

Calculation of prompt fission neutron spectra for 235U(n,f)

The prompt fission neutron spectra for the neutron-induced fission of ²³⁵U at E_n < 5 MeV are calculated using nuclear evaporation theory with a semi-empirical model, in which the nonconstant and constant temperatures related to the Fermi gas model are taken into account. The calculated prompt fission neutron spectra reproduce the experimental data well. For the n(thermal)+²³⁵U reaction, the average nuclear temperature of the fission fragment, and the probability distribution of the nuclear temperature, are discussed and compared with the Los Alamos model. The energy carried away by γ rays emitted from each fragment is also obtained and the results are in good agreement with the existing experimental data.     

Study of Nuclear Level Structure in Tc Isotopes with Mass A～100

In the present work, the structures of the excited positive/negative-parity yrast states of ¹⁰¹Tc are discussed by using a projected shell model, and a band diagram calculated for the positive-parity yrast band is also shown in order to extract physics out of numerical results. In addition, the analysis of other three bands originated from 3/2^－[301], 5/2^－[303], and 1/2⁺[431] Nilsson states, respectively, is also performed in the framework of this model. Until recently, very little property about the N=52—54 intermediate nuclei in the Z～42—44 region has been known. In order to understand these "transitional nuclei", we select the nucleus ⁹⁵Tc as an example. So in this work, we also present our investigation of the level structure in the ⁹⁵Tc nucleus.     

New Low-spin Levels in 76Se and Discussion of Its Yrast Band Structure

The decay of bromine–76 was studied using compton–suppressed spectrometer and high–purity ge detectors in singles and coincidence mode, respectively. bromine–76 was produced via two reactions,i. e.,⁷⁵As(α,3n)⁷⁶Br and ⁷⁶Se(p, n)⁷⁶Br.the results of these experiments verified the previously reported levels and gammas of ⁷⁶Se. in addition to the previously described transitions and levels, 39 new γ–rays and 15 new energy levels were found for the first time. spins and parities for new levels are proposed based on the calculated logft values, de–excitation modes of the observed states, and some nuclear reaction experiment results. a new decay scheme of ⁷⁶Br is proposed in the present work. combining with the high–spin states observed by the in–beam γ–ray spectroscopy of a previous decay work, the positive–parity yrast states were compared with the results from calculations in the framework of the projected shell model.     

"ONE,TWO, INFINITY" MODEL FOR PRECOMPOUND REACTION AND NUCLEAR SIZE EFFECT

The influence of limited nuclear size effect to "One, two, infinity" model for precompound reactions is discussed. The inclusive proton spectra in ⁵⁸Ni, ⁹⁰Zr, ²⁷Al(p,p') reactions and the inclusive neutron spectra from ²⁷Al(p,n) reaction at 90 MeV are calculated. The results are in a good agreement with the data.     

Theoretical Analysis of Double Differential Cross Sections for n+ 238U Reaction

Based on the new measurements of total, nonelastic, elastic cross section and elastic scattering angular distributions for n+U reactions, a set of neutron optical model potential parameters is obtained in the region of incident neutron energy from 0.1 to 20 MeV. The cross sections, angular distributions, energy spectra and double differential cross sections are calculated and analyzed by optical model, nuclear fission theory, distorted wave Born approximation theory, coupled channel theory, the unified Hauser-Feshbach theory, as well as exciton model. The results indicate that our theoretical model can reasonably analysis n+ ²³⁸U reaction data with neutron energy lower than 20 MeV.     

Identification of High-Spin States in Odd-Odd 126I

Excited states in odd–odd ¹²⁶I have been studied via the heavy–ion induced fusion–evaporation reaction ¹²²Sn(¹¹B,5n2p) at beam energies of 55 and 60 MeV with beams provided by the HI–13 tandem accelerator of CIAE in Beijing.A level scheme consisting of 20 new γ transitions assigned to ¹²⁶I is established.The assignment of the established level scheme to ¹²⁶I is based on the observed coincidences between the newly identified γ–transitions and two previously known cascade γ transitions feeding the ground state of ¹²⁶I, and supported by a cross measurement using the ¹²⁴Sn(^7lI,5n) reaction performed at UTTAC,Japan.The observed structures of ¹²⁶I at high spins show typical properties of collective rotation in a deformed nucleus. their possible configurations are discussed briefly on the basis of knowledge from the neighboring nuclei.     

THE CROSS SECTION MEASUREMENT FOR THE 107Ag(n,2n)106mAg REACTION

The cross section for 107Ag(n,2n)^106mAg has been measured by using the activation method relative to the cross section of ²⁷Al(n,α)²⁴Na in the neutron energy range of 13.50—14.73MeV.The values of 469±22,480±22,503±24,538±25,555±25,572±26mb were obtained at the 13.50,13.60,13.90,14.10,14.35,and 14.73MeV neutron energy,respectively.The results are compared with the published data.The neutron energies were determined by activity ratios of Nb and Zr foils.     

Cross Section Measurements for (n,2n),(n,p)and (n,α) Reactions on Strontium Isotopes at the Neutron Energy About 14MeV

Cross-sections for ⁸⁴Sr(n, 2n)⁸³Sr, ⁸⁶Sr(n, 2n)^{85mSr,86Sr(n, 2n)85Sr,88Sr(n, 2n)87mSr,84Sr(n, p)84Rb,86Sr(n, p)86Rb, 88Sr(n, p)88Rb and 88Sr(n,α)85mKr reactions were measured at neutron energies from 13.5 to 14.6MeV using activation technique and γ-ray spectrometry. The neutron flux was determined using the monitor reaction 93Nb(n, 2n)92mNb and the neutron energies were measured by the method of cross section ratios for $^{90}$Zr(n, 2n)$^{89m+g}$Zr to $^{93}$Nb(n, 2n)$^{92m}$Nb reactions. The results of present work were compared with data published previously.}     

Three-Body Model of 11Li

A new effective interaction between a neutron and the ⁹Li core is introduced, and based on the n+n+⁹Li model, a variational calculation on the neutron rich nucleus ¹¹Li is completed. The one-body density, formfactor and shapedensity are investigated, The RMS radius and the binding energy are also calculated and are in good agreement with the experimental data.     

Study of Multi-Quasiparticle Excited States in 139Ce

High-spin states in ¹³⁹Ce have been populated using the ¹³⁰Te(¹²C,3n) reaction at beam energy of 50MeV. The level scheme of ¹³⁹Ce has been revised and extended greatly up to E=5765.0keV. The level structure of ¹³⁹Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in ¹³⁹Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.     

MEASUREMENT OF ISOMERIC CROSS-SECTION RATIO IN 133Cs(n,γ) 134Cs REACTION

The isomeric absolute cross-section have been measured for the reaction ¹³³Cs (n,c) ¹³⁴ Cs at 14.8 MeV neutron energy.The results are:σ_n,γ^134mCs=1.76±0.14mb;σ_n,γ^134gCs=5.17±0.41mb;σ_n,γ^134+gCs=6.93±0.55mb.The isomeric cross-section ratio is σ^134m_Cs/σ^134gCs=0.34±0.03 The experimental results are in agreement with the values given by S.M. Qaim andcompared with the theoretical results calculated by Huizenga-Vandenbosch theory.From this, the spin cut-off paramenter σ and the number of γ-Cascades have been de-termined.     

Possible Way to Synthesize Superheavy Element Z=117

Within the framework of the dinuclear system model, the production of superheavy element Z = 117 in possible projectile-target combinations is analysed systematically. The calculated results show that the production cross sections are strongly dependent on the reaction systems. Optimal combinations, corresponding excitation energies and evaporation channels are proposed, such as the isotopes^248.249 Bk in ^48 Ca induced reactions in 3n evaporation channels and the reactions ^45Sc＋246.248Cm in 3n and 4n channels, and the system ^51 V＋ 244pu in 3n channel.