The 64Ni(6Li,d)68Zn reaction

The ⁶⁴Ni(⁶Li, d)⁶⁸Zn reaction has been studied at 28 MeV bombarding energy. For several low-lying states in ⁶⁸Zn, S-values extracted via DWBA analysis are compared with shell model and collective model (IBA) predictions.     

Lifetimes of some excited states in 64Ni, 66Zn and 68Zn

Mean lives and excitation energies of the lowest levels in⁶⁴Ni,⁶⁶Zn and⁶⁸Zn were measured with the aid of the (α, α′γ) and (α, pγ) reactions. The γ-rays were detected in coincidence with the outgoing particles. The following mean lives were determined from DSA measurements: 400 ± 150 fs for the level at E_x = 1.35 MeV in ⁶⁴Ni; 270 ± 100, 210 ± 110, 330 ± 200, 80 ± 70 fs for the levels at E_x = 1.87, 2.45, 2.83, 2.94 MeV in ⁶⁶Zn, and 1300 ± 300, > 160, 600 ± 200 fs for the levels at E_x = 1.08, 1.89 and 2.76 MeV in ⁶⁸Zn, respectively.     

Elastic and inelastic scattering of 178 MeV protons from 58Ni and 60Ni

The elastic and inelastic scattering of 178 MeV protons from ⁵⁸Ni and ⁶⁰Ni has been studied. Angular distributions were measured for the differential cross sections for elastic scattering as well as inelastic scattering from excited states below about 5 MeV, all with natural parity. For the elastic and for the inelastic scattering from the first excited state (2⁺ in both nuclei, the angular distributions for the polarization were also measured. The measurements extend out to c.m. angles of about 60°, corresponding to a momentum transfer of about 600 MeV/c.The elastic and inelastic scattering data were compared to the results of coupled-channel calculations in the vibrational model using a deformed spin-orbit interaction of the full Thomas form. Good agreement was found in general showing that the main features of the experimental results are well described in this model.     

High-spin states in 58Ni

High-spin states of ⁵⁸Ni were investigated via the study of in-beam γ-ray induced by the compound reaction ⁴⁸Ti(¹²C, 2n)⁵⁸Ni between 26 and 48 MeV. The energies and decay modes of these levels were determined from the analysis of γ-γ coincidence measurements at 35 MeV. The most intense lines in the ⁵⁸Ni γ-ray spectrum correspond to a cascade to the ground state, through levels at 1.454, 2.459, 3.619 and 4.381 MeV, also fed in other reactions, and by two previously unknown levels at 5.125 and 5.662 MeV; the spin assignments based on the present study are (apart from the ground state) 2, 4, 4, 5, 6 and 7 respectively for these levels. The first three were already known and the last three are new. The mixing ratios for the transitions between these levels are also determined. We observe also the same cascade in the reaction ⁵⁶Fe(α, 2n)⁵⁸Ni at an incident energy 18–24 MeV. Comparisons with other reactions, previous studies and recent shell-model calculations are presented.     

Yrast cascade in 60Ni

Yrast levels of ⁶⁰Ni were investigated via the study of in-beam γ-rays induced by 15–25 MeV α-partictes on ⁵⁸Ni, 26–48 MeV ¹²C ions on ⁵⁰Cr and 30–60 MeV ¹⁶O ions on ⁴⁶Ti. The compound nucleus formed by these target-projectile combinations is ⁶²Zn, and its decay by two-proton emission populates yrast levels of ⁶⁰Ni. The ordering and decay modes of the yrast levels were determined from the analyses of in-beam γ-ray angular distribution and γ-γ coincidence measurements. The new levels established are at 4.262, 5.345 and 6.807 MeV. These together with the known 2₁⁺ (1.332 MeV) and 4₁⁺(2.505 MeV) levels constitute the yrast cascade. The spin assignments based on the present study are 6, 7, 9 for the 4.262, 5.345 and 6.807 MeV levels, respectively. The excitation functions for the yrast γ-rays from the ⁵⁰Cr(¹²C, 2p)⁶⁰Ni reaction show peaks near 33 MeV incident energy.     

High-spin states in 59Ni

High-spin states in ⁵⁹Ni have been investigated via the study of in-beam γ-rays following the reactions ⁵⁰Cr(¹²C, 2pn)⁵⁹Ni (26–58 MeV) and ⁵⁶Fe(α, n)⁵⁹Ni (10, 15, 22.5 MeV). The spins of previously known levels have been confirmed or determined for the first time, in particular for those at $\text{3376.8}\text{keV}\text{(J =}\text{11}\text{2}\text{)}\text{and}\text{4141.3}\text{keV}\text{(J =}\text{13}\text{2}\text{or}\text{15}\text{2}\text{)}$. New states have been established and their spin determined, at $\text{1739.2}\text{keV}\text{(J =}\text{9}\text{2}\text{), 2349.2}\text{keV}\text{(J =}\text{11}\text{2}\text{), 2535.5}\text{keV}\text{(J =}\text{13}\text{2}\text{), 4455.4}\text{keV}\text{(J =}\text{13}\text{2}\text{), 4947.5}\text{keV}\text{(J =}\text{15}\text{2}\text{)}\text{and}\text{5251.7}\text{keV}\text{(J =}\text{13}\text{2}\text{or}\text{15}\text{2}\text{)}$. The resulting ⁵⁹Ni decay scheme is discussed in the framework of nuclear models.     

40Ca+58Fe,58Ni反应中的径向膨胀流研究

利用同位旋相关的Boltzmann-Langevin方程研究了⁴⁰Ca+⁵⁸Fe和⁴⁰Ca+⁵⁸Ni两个反应系统在53,100,150和200MeV/u入射能量下对心碰撞的径向膨胀流.发现对于丰中子系统⁴⁰Ca+⁵⁸Fe的径向膨胀流系统性地小于稳定系统⁴⁰Ca+⁵⁸Ni的径向膨胀流.在假定轰击能量与反应体系的压缩密度呈抛物线关系时,能够解释入射能量和径向膨胀流之间呈现的直线关系.提取了出现径向膨胀流的轰击能量阈值,发现对丰中子系统⁴⁰Ca+⁵⁸Fe得到的能量阈值小于稳定系统⁴⁰Ca+⁵⁸Ni所得到的能量阈值.     

The charge density of 58Ni

The charge density of ⁵⁸Ni is deduced from elastic electron scattering data by the “model-independent” method of Friar and Negele. This density is compared with results of the Saclay group, and also with density-dependent Hartree-Fock calculations.     

Study of the 58Ni(τ, α)57Ni reaction at 25 MeV

The ⁵⁸Ni(τ, α)⁵⁷Ni reaction has been studied at 25 MeV incident energy. Angular distributions have been measured from 5° to 50° with a split-pole spectrometer up to 13.5 MeV excitation energy. A local zero-range DWBA analysis has been carried out, allowing l-assignments for about eighty levels, most of them previously unknown. An isospin-dependent potential has been used in the calculation of the neutron form factor for both T_<and T_> states, and the C²S values deduced using this procedure are compared to those obtained with the usual separation energy method. Analog states of eleven ⁵⁷Co levels have been identified and the eventuality for isospin mixing in ⁵⁷Ni has been discussed. A sum rule analysis has been carried out and energy centroids of hole states have been determined. About 60% of the $\text{1}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{2}\text{s}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{T}{}_{\mathrm{<}}$ strengths and the full $\text{1}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ and $\text{1}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ hole strengths are observed. It is shown that the two excess neutrons in the ⁵⁸Ni ground state mainly populate the $\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{, 1}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ orbitals, whereas the occupancy number of the $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ subshell is found to be smaller than 0.1%. Some non-pickup angular distributions have also been observed and a CRC analysis assuming two-step processes in the (τ, α) reaction and weak-coupling wave functions for final states has been attempted. Assignments of J^π values are proposed for four ⁵⁷Ni levels, based on this analysis.     

Investigation of the 58Ni(7Li, 6Li)59Ni reaction with vector polarized 7Li

Angular distributions of the cross section and of the vector analyzing power for the ⁵⁸Ni(⁷$\text{Li}$, ⁶Li)⁵⁹Ni reaction leading to several groups of levels in the final nucleus have been measured at E_Li = 20.3 MeV. The observed Q-value dependence of the vector analyzing power can to a large extent be attributed to a kinematical effect caused by the polarization of the orbital angular momentum of the transferred neutron in ⁷Li.     

Gamma transitions in 59Ni following the β+ decay of 59Cu

The γ-ray decay spectrum of 82 s ⁵⁹Cu produced by the ⁵⁸Ni(p, γ) ⁵⁹Cu reaction has been studied with a 40 cm³ Ge(Li) detector. The number of γ-rays now known for this decay has more than doubled. Additional direct β⁺ branches to the 1679.7($\text{5}\text{2}{}^{\mathrm{?}}$), 2414.8($\text{3}\text{2}{}^{\mathrm{?}}$) and 2681 keV states of ⁵⁹Ni have been identified with log ft values of 5.5, 5.5 and 6.0, respectively. A major change is the reassignment of the 1340.4 keV γ-ray to a 1679.7 → 339.3 keV transition. A limit of log $\text{ft ≧ 6.9}$ is given for the direct feeding of the 1337($\text{7}\text{2}{}^{\mathrm{?}}$) keV state, together with limits for direct population of other energetically available states. The new weak γ-ray branches found for the 878.0, 1301.5 and 1679.7 keV levels are in excellent agreement with the recent theoretical calculations of Glaudemans et al.     

Angular distribution of 1.04 GeV protons scattered by 12C, 58Ni, 208Pb

Angular distribution measurements for elastic and inelastic scattering of 1.04 GeV proton by ¹²C, ⁵⁸Ni and ²⁰⁸Pb with an energy resolution of the order of 100 keV are presented.     

Coincidence spectroscopy of pion-nucleaus interactions in 60Ni

The preevaporation phase of the interaction of 70 MeV pions with ⁶⁰Ni has been studied by measuring multinucleon removal spectra via prompt γ-ray spectra in coincidence with energetic charged particles. The data provide a direct estimate of the reaction cross section due to inelastic scattering and of the multiplicity of energetic protons emitter by the excited nucleus.     

Charge density and single-particle structure of 58Ni

The charge distribution of ⁵⁸Ni has been calculated by summing the squares of the proton wave functions in a one-body non-local potential whose parameters were adjusted to give the experimental centroid energies. The squared wave functions were weighted by the occupation numbers. A definite procedure to solve the problems connected with the state dependence of such a potential has been developed. The calculated ⁵⁸Ni charge density depends essentially on the ld state centroid energy and on the 1f_{$\text{7}\text{2}$} occupation number. These have been determined by a fit to the experimental charge density.     

New neutron-deficient tellurium,iodine, and xenon isotopes produced by reactions of 290 MeV 58Ni ions on 58Ni and 63Cu targets

The new neutron-deficient nuclei ^108–110Te, ^110–114I, and ¹¹⁴Xe were produced as evaporation residues from reactions of 290 MeV ⁵⁸Ni ions on ⁵⁸Ni and ⁶³Cu targets and identified by mass separation and subsequent decay spectroscopy. The isotopes ¹⁰⁸Te, ¹⁰⁹Te, ¹¹⁰I, and ¹¹¹I form a new region of α-particle decay. The decay data are compared with predictions for nuclear masses and half-lives.     

Spectroscopy of 62Ni with the 61Ni(d, p) reaction

Differential cross sections, vector and tensor analysing powers have been measured for the ⁶¹Ni(d, p) reaction at a deuteron energy of 12.3 MeV. Most of the 30 transitions observed below 8.5 MeV excitation are dominated by a single j-value, which was determined from behaviour of the analysing power data. For a number of transitions it was possible to make unambiguous j-assignment relying on the established j-dependence of the T₂₂ tensor analysing power. The deduced spectroscopic factors indicate that the full strength of neutron transfer to the ($\text{2p, 1f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}$) and $\text{1}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ orbits was found and seven $\text{5}\text{2}{}^{\mathrm{+}}$ transitions were located above 5.3 MeV. The separated strengths of the $\text{3}\text{2}{}^{\mathrm{?}}\text{,}\text{1}\text{2}{}^{\mathrm{?}}\text{and}\text{5}\text{2}{}^{\mathrm{?}}$ transitions are compared with shell-model calculations for the low-lying states of ⁶²Ni.     

Microscopic study of elastic 28Si28Si scattering and intermediate structure resonances in 56Ni

Elastic ²⁸Si²⁸Si scattering has been studied microscopically with special emphasis on quasimolecular and barrier resonances in high partial waves. Schematic application of the double resonance mechanism predicts intermediate structures in the excitation functions in qualitative agreement with the experimental data.     

Decay of the compound nucleus 74Kr formed in the reaction 16O + 58Ni

Gamma-ray and charged-particle emission has been studied after bombardment of ⁵⁸Ni with ¹⁶O at energies from 44.5–76.5 MeV. The excitation functions for various reaction channels have been measured. The locus in energy and spin of maximum cross section (the entry line) of the γ-emitting region in the 2pγ and 3pγ channels have been studied through measurement of γ-ray multiplicity, average particle energy and average γ-ray energy. The standard deviations in both energy and spin of the distributions of cross section are presented. Statistical model calculations including shell corrections in the level density show very satisfactory agreement with the experimental results. The moment of inertia at high spin and excitation energy is deduced from the measured entry line.