The Cross Section Measurement for the Reactions of 48,46Ti(n,p) 48,46Sc 50Ti(n,α) 47Ca and 58Ni (n,2n) 57Ni 58Ni(n,p)58m+gCo

The cross sections for the ⁵⁰Ti(n,α)⁴⁷Ca,⁴⁶Ti(n,p)⁴⁶Sc、⁴⁸Ti(n,p)⁴⁸Sc and ⁵⁸Ni(n,2n)⁵⁷Ni ⁵⁸Ni(n,p)^58m+gCo reactions have been measured by using the activation method relative to the cross sections of the ²⁷Al(n,α)²⁴Na reaction in the neutron energy range of 13.50—14.81MeV.The neutron energies were determined by the cross section ratios of the ⁹⁰Zr(n,2N) ^89m+gZr and ⁹³Nb (n,2n) ^92mNb reactions.The results obtained are compared with the published and to be published data of several authors.     

Isomeric cross sections for the (n, 2n) reaction on 82Se, 81Br,and 45Sc at 15.1 MeV

Activation techniques have been used to measure the cross sections at 15.1 MeV neutron energy for the following reactions: ⁸²Se(n, 2n)^81m+gSe, ⁸¹Br(n, 2n)^80m+gBr, and ⁴⁵Sc(n, 2n) ^44m+gSc. Isomeric cross-section ratios were evaluated by applying the method of least squares to the time behavior of γ-ray activity following the ground-state decay of each isomeric pair. The absolute cross section σ_m for the formation of the metastable state was measured by the mixed-powder method with the ²⁷Al(n, α)²⁴Na reaction as the monitor. The cross section σ_g for the formation of the ground state was then determined by using the isomeric cross-section ratio. The sum of σ_m and σ_g for each reaction is compared with the theoretical value obtained from calculations based on the statistical model for the formation of a compound nucleus and its subsequent emission of neutrons.     

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.}     

Activation cross-sections of titanium isotopes at neutron energies of 13.5–14.8 MeV

The cross-sections for ~(46) Ti(n,2 n)~(45) Ti, ~(46) Ti(n,p)~(46 m+g) Sc+~(47) Ti(n,d*)~(46 m+g) Sc, ~(46)Ti(n,p)~(46 m+g) Sc, ~(47) Ti(n,p)~(47) Sc+~(48) Ti(n,d*)~(47) Sc, ~(47) Ti(n,p)~(47) Sc, ~(48) Ti(n,p)~(48) Sc+~(49) Ti(n,d*)~(48) Sc,~(48) Ti(n,p)~(48) Sc, and ~(50) Ti(n,α)~(47) Ca reactions were investigated around neutron energies of 13.5–14.8 Me V by means of the activation technique. Fast neutrons were produced by the~3 H(d,n)~4 He reaction. Neutron energies from different directions in the measurements were obtained in advance using the method of cross-section ratios for ~(90) Zr(n,2 n)~(89 m+g) Zr and ~(93) Nb(n,2 n)~(92 m) Nb reactions. The results obtained are analyzed and compared with the experimental data provided by the literature and verified nuclear data in the JEFF-3.3,CENDL-3.1, ENDF/B-VIII.0 libraries, as well as results calculated by Talys-1.9 code.     

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.     

CROSS SECTION MEASUREMENTS OF NUCLEAR REACTIONS FOR Ni INDUCED BY 14MeV NEUTRONS

The cross sections of reactions ⁵⁸Ni(n,2n)⁵⁷Ni,⁵⁸Ni(n,p)^58mCo,⁵⁸Ni(n,p)^58gCo and ⁵⁸Ni(n,p)^58m+gCo were measured based on ²⁷Al(n,a) ²⁴Na reaction by activation methods.Incident neutron energies were 14.10MeV and 14.62MeV.A comparison was made between present results and other published data.The cross sections for ^58gCo nuclei formation are given for the first time.     

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.     

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 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.     

Cross-section measurement for the ~(93)Nb(n,2n)~(92g)Nb reaction at the neutron energy of 14.6 MeV by the AMS method

The cross-section for the~(93)Nb(n,2n)~(92g)Nb reaction has been measured at the neutron energy of 14.6 Me V using neutron activation and accelerator mass spectrometry(AMS)determination of the long-lived product nuclide~(92g)Nb.The neutron energy was generated from the D+T neutron source at the China Institute of Atomic Energy(CIAE).The neutron flux was monitored by measuring the activity of~(92m)Nb produced in the competing reaction channel of~(93)Nb(n,2n)~(92m)Nb.At the neutron energy of 14.6 MeV,the~(93)Nb(n,2n)~(92g)Nb reaction cross-section of(736±220)mb was obtained for the first time.     

Cross Section Measurements for (n,d*)(n,t) and (n,n'α) Reactions

Cross sections for some (n,d*),(n,t) and (n,n'α)reactions have been measured by using the activation method relative to cross sections of ²⁷Al(n,α)²⁴Na or ⁹³Nb(n,2n)^92mNb reactions in neutron energies around 14MeV.In this paper some of the published cross section data have also been listed and compared with our results.The neutron energies were determined by the method of cross section ratios for the reactions of ⁹⁰Zr(n,2n) ^89m+gZr and ⁹³Nb(n,2n)^92mNb.     

Alpha-induced reactions on cobalt

Alpha-induced reactions on the target element cobalt were investigated in the energy region from 25 to 172.5 MeV using the stacked foil technique. Twenty excitation functions were measured for the production of ⁶¹Cu, ⁵⁷Ni, ^60m+gCo, ^58m+gCo, ⁵⁷Co, ⁵⁶Co, ⁵⁵Co, ⁵⁹Fe, ⁵²Fe, ⁵⁶Mn, ⁵⁴Mn, ^52m+gMn, ⁵¹Cr, ⁴⁸V, ⁴⁷Sc, ^46m+gSc, ^44mSc, ^44gSc, ⁴³K and ⁴²K. Only for ⁶¹Cu, ⁵⁸Co, ⁵⁷Co and ⁵⁶Mn were cross sections available earlier, which, however, were limited to α-energies ≦ 41 MeV. The experimental data are compared with calculations considering equilibrium as well as preequilibrium reactions according to the hybrid model of Blann. The excitation functions of half the product nuclides are dominated by preequilibrium effects over wide energy ranges. From the reaction ⁵⁹Co(α, 2n)⁶¹Cu an initial exciton number between n₀ = 4 (2n-2p-0h) and n₀ = 5 (2n-3p-0h) or (3n-2p-0h) is deduced. However, the theoretical analysis reveals several severe shortcomings, e.g. the underestimation of the excitation functions for ^60m+gCo, ^58m+gCo and ⁵⁹Fe for up to 2 orders of magnitude. For ^60m+gCo the discrepancy between theory and experiment can be attributed to break-up reactions of the α-particle, whereas for the two other product nuclides even more complex reaction mechanisms have to be assumed. Moreover, the strong contributions of preequilibrium emission of α-particles observed for (α,2pxn) and (α, 4pxn), which are not accounted for by the program OVERLAID ALICE, indicate that the initial reaction phase for α-induced reactions is more differentiated than is supposed by the present form of the hybrid model.     

The Cross Section Measurements for the 100Mo(n2n)99Mo,96Mo(n,p)96Nb and 92Mo(n,α)89m+gZr Reactions

The cross sections for ¹⁰⁰Mo(n2n)⁹⁹Mo,⁹⁶Mo(n,p)⁹⁶Nb and ⁹²Mo(n,α)^89m+gZr have been measured by using the activation method relative to the cross sections of ²⁷Al(n,α)²⁴Na in the neutron energy range 13.40—14.79MeV.The comparison between the values of measured and calculated using theory mode was made.The evaluated excition functions for the three reactions are given.     

RESEARCH ON THE 88Y(n,2n) REACTION CROSS SECTION

The cross sections of the neutron induced (n,2n) reaction an the unstable target nucleus ⁸⁸Y in the energy range from 10.3 to 17.4MeV are obtained from the measurement of the ⁸⁷Sr (d,2n) reaction.This work is based on the hypothesis that the formation of the Compound nucleus is independent of its decay.The results are compared with our calculated results and the experimental data and calculated result of Prestwood and his co-worker.The comparison indicates that this work is worthy for further study.     

Critical consideration of the statistical model analysis of photonuclear isomeric cross-section ratios

We have measured isomeric cross-section ratios for the photonuclear reactions ¹⁸¹Ta(γ, 3n) ^178m,gTa, ¹⁴²Nd(γ, n)^141m,gNd, ¹¹⁰Pd(γ, n)^{109m₁,m₂,g}Pd, ¹⁰⁸Pd(γ, n)^107m₁,m₂Pd, ¹⁰⁰Mo(γ, n) ^99m,gMo, ⁹²Mo(γ, n)^91m,gMo and ⁸⁹Y(γ, n)^88m₁,m₂Y. The experimental results were compared with statistical model calculations according to the method of Huizenga and Vandenbosch. The applicability and limits of this method, especially the simple decision model for the population of the isomeric state and the ground state of the residual nucleus, were tested and discussed. Additionally, it is shown that for photonuclear reactions on magic nuclei, contributions of a direct reaction mechanism are not negligible.     

Measurements of g-Factor of Rotational Band States in 82Sr

The g-factors of the positive parity rotational states up to spin I = 8^＋ for the ground state band in even-even nuclei S2Sr have been measured by a transient-magnetic-field ion implantation perturbed angular distribution method. The experimentally measured 9-factors increase with the increasing spin along the band and show that the g9/2 proton aligns only and the alignment starts from I =6^＋. The measured g-factors also indicate that the nuclei ^82Sr gain their spins by the quasi-proton alignment at higher spin.     

Measurement of 125Ba High Spin States

The high spin states of ¹²⁵Ba populated via the ¹⁰⁹Ag(¹⁹F,3n) reaction are measured by using a BGO Compton suppressed HPGe detector array.The negative and positive parity bands built respectively on the h_11/2 and g_7/2 neutron hole states are extended to 35/2^－ and 23/2⁺.Backbending occurs in both signature branches of the negative band at the frequencies close to that of the ¹²⁴Ba yrast band.An onset of backbending in the positive band has been seen.     

Gluon Exchange Potential and Cross-Section for pp→ΛΛ Proce

One and two-gluon exchange potentials (OGEP and TGEP) relevant to the pp→ΛΛ transition process are derived from the S-matrix in the a　roximation of order p²/m². An effective transition potential obtained from these gluon exchange potentials by the constituent quark model is employed to calculate the differential and total cross-sections for the pp→ΛΛ reaction in the plane wave Born Approximation.The calculated result shows that the relativistic correction terms in the OGEP and TGEP give considerable improvements on the cross-section in comparison with the previous calculations performed by making use of the OGEP given in the extremely non-relativistic a　roximation.     

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.     

Effect of entrance channel parameters on the fusion of two heavy ions: Excitation functions of reaction products in16O +66Zn and37Cl +45Sc reactions

Excitation functions of reaction products formed in¹⁶O +⁶⁶Zn and³⁷Cl +⁴⁵Sc systems, leading to the same compound nucleus,⁸²Sr, were measured using recoil-catcher technique and off-line γ-ray spectrometry. The contribution of non-compound processes like transfer and incomplete fusion (ICF) reactions to the cross-sections of different evaporation residues were delineated by comparing the experimental data with the predictions of Monte Carlo simulation code PACE2. The results show that non-compound processes become a significant fraction of the total reaction cross-section in¹⁶O +⁶⁶ systems in the beam energy range studied, while³⁷Cl +⁴⁵Sc gives mainly compound nucleus products. The mass asymmetry dependence of the fusion and non-compound cross-sections have been analysed in terms of the static fusion model and sum rule model