The 26Mg(14N, 10B)30Si and 26Mg(14N, 11B)29Si reactions

Reactions induced by ¹⁴N on ²⁶Mg at bombarding energies of 60–95 MeV have been studied. Angular distributions for states populated in ²⁹Si by the (¹⁴N, ¹¹B) reaction and in ³⁰Si by the (¹⁴N, ¹⁰B) reaction have been compared with Hauser-Feshbach and DWBA calculations to determine the reaction mechanism and to deduce spectroscopic information. The cross sections for the states populated in ²⁹Si and ³⁰Si are in poor agreement with statistical model calculations, indicating a non-compound nucleus mechanism.     

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 12C(18O, α)26Mg and 12C(18O, 8Be)22Ne reaction

Excitation functions for α-emission leading to the ground and first excited states of ²⁶Mg and ⁸Be emission leading to the ground and first and second excited states of ²²Ne have been measured at several forward angles for E_c.m. = 15 to 22.4 MeV. There is little evidence for correlated structure. The angular distribution at 16.5 MeV for the α + ²⁶Mg(g.s.) channel is rather structureless while that for the ⁸Be+²²Ne(g.s.) channel appears to be dominated by a J = 13 contribution. Statistical model calculations indicate that much of the yield for both the α and ⁸Be exit channel is compound nuclear in origin, with some indication of a larger direct contribution for the ⁸Be channel at the lower end of the bombarding energy range.     

Reactions of 40Ar with 159Tb, 142Nd and 144Sm; New α-activities from 189Bi, 173Pt and 177Au

Reactions of ⁴⁰Ar ions with targets of ¹⁵⁹Tb, ¹⁴²Nd, and ¹⁴⁴Sm have been studied at energies below 300 MeV with a helium gas-jet system. Excitation functions for (Ar, xn) reactions, where x = 5–10, were obtained for the radioactive products that decay by α-emission. Based on the characteristics of these excitation functions and on the systematics of α-decay, evidence is presented for the existence of the nuclides ¹⁸⁹Bi with α-particle energy E_α = 6.67±0.01 MeV and half-life < 1.5 sec, and ¹⁷³Pt with E_α = 6.19±0.01 MeV; and for the emission from ¹⁷⁷Au of an α-particle with E_α = 6.15±0.01 MeV.     

Atomic antiproton states in 16O, 18O, 32S, 40Ca, 44Ca and 122Sn

Atomic levels for the systems p? plus ¹⁶O, ¹⁸O, ³²S, ⁴⁰Ca, ⁴⁴Ca and ¹²²Sn are calculated in optical potentials based on the N?N interaction of Dover and Richard.     

Statistical fluctuations and compound elastic scattering for 12C(12C, 12C)12C and 16O(16O, 16O)16O

The difference between the observed fluctuations in the elastic excitation functions for carbon-carbon and oxygen-oxygen scattering, just above the Coulomb barrier, is interpreted in terms of the compound nucleus model.     

15N excitation contribution to 48Ca(16O, 15N)49Sc reaction

The effect of ¹⁵N excitation process is studied in the reaction ⁴⁸Ca(¹⁶O, ¹⁵N)⁴⁹Sc. The excitation process is included into a generalized non-local optical potential for a scattersing ¹⁵N-⁴⁹Sc and is found to be responsible for a shift of a grazing peak in the exact finite-range DWBA calculation.     

Spin assignments from the 142Nd(7Li, 6He)143Pm and 144Sm(7Li, 6He)145Eu reactions at 52 MeV

Angular distributions have been measured for transitions to low-lying states in ¹⁴³Pm and ¹⁴⁵Eu populated by the ¹⁴²Nd(⁷Li, ⁶He)¹⁴³ and the ¹⁴⁴Sm(⁷Li, ⁶He)¹⁴⁵Eu reactions at $\text{E(}{}^7\text{Li}\text{) = 52}$ MeV. Elastic scattering of ⁷Li at 52 MeV on ¹⁴²Nd and ¹⁴⁴Sm, and ⁶Li at 46 MeV on ¹⁴²Nd and at 45 MeV on ¹⁴⁴Sm, were measured. Optical-model parameters extracted from fits to the scattering data were used in a finite-range DWBA analysis of the angular distributions for levels below 1.40 MeV excitation energy in ¹⁴³Pm and 1.84 MeV in ¹⁴⁵Eu. The reaction cross sections forward of 6° c.m. allow unambiguous distinction to be made between 2d_{$\text{5}\text{2}$} and 2d_{$\text{3}\text{2}$} final states. Final-state spins have been assigned to d-states in ¹⁴³Pm at 1.40 MeV($\text{3}\text{2}$⁺)and in ¹⁴⁵Eu at 1.042 MeV ($\text{3}\text{2}$⁺). Existing assignments to other levels in both residual nuclei have been confirmed.     

12C1 and 8Be production in 12C + 208Pb collisions

The mechanisms involved in the production of fast α-particles in ¹²C-induced reactions have been studied for the ¹²C + ²⁰⁸Pb system at the bombarding energies of E_12c = 132, 187 and 230 MeV. Absolute cross sections for the reactions ²⁰⁸Pb(¹²C. ¹²C¹→α + ⁸Be), ²⁰⁸Pb(¹²C, ⁸Be(g.s.)) and ²⁰⁸Pb(¹²C, ⁸Be(2.94 MeV)) have been determined by coincidence measurement of two or three correlated α-particles. Inclusive α-particle production cross sections were also measured at E_12c = 187 MeV. It is found that the inelastic process (¹²C, ¹²C¹→α + ⁸Be) does not contribute significantly to fast α-particle production but that the production of ⁸Be by projectile fragmentation is an important source of α-particles. At the highest bombarding energy (230 MeV) it appears that the ¹²C → 3α fragmentation reaction becomes more prominent at the expense of the ¹²C→α + ⁸Be fragmentation channel.     

12C(7Li,t)16O和20Ne(d,6Li)16O反应的研究

本文把用于处理重离子引起的单粒子转移反应的Goldfarb-Buttle方法推广到多粒子转移反应。计算了¹²C(⁷Li,t)¹⁶O和²⁰Ne(d,⁶Li)¹⁶O反应,用了¹⁶O的全相干波函数,考虑了某些反冲因素,并将结果与实验作了比较。     

The α-transfer reactions 27Al(6Li,d)31P, 29Si(6Li,d)33S and 31P(6Li,d)35Cl at 36 MeV

The α-transfer reactions ²⁷Al(⁶Li, d)³¹P, ²⁹Si(⁶Li, d)³³S and ³¹P(⁶Li, d)³⁵Cl have been studied at a ⁶Li energy of 36 MeV. Absolute cross sections and angular distributions have been measured and an exact finite-range distorted-wave Born approximation analysis assuming a direct cluster transfer has been used to extract from the data α-particle spectroscopic strengths for levels populated in ³¹P, ³³S and ³⁵Cl in the three reactions respectively. The results show that in the case of most of the low-lying excited states of ³¹P, a single value of L of the transferred α-particle contributes, though a multiplicity of L-values are allowed by angular momentum selection rules. It is also found that the α-particle spectroscopic strength of the ground state of ³¹P is a factor of 2 more than the strengths of the ground states of ³³S and ³⁵Cl. The α-spectroscopic strengths of ground states of these, as well as other odd-A s-d shell nuclei, are compared with the presently available shell model calculations.     

Charge exchange reaction 14C(6Li, 6He)14N

Angular distributions of the charge exchange reaction ¹⁴C(⁶Li, ⁶He)¹⁴N leading to the 1⁺ ground state and 3.95 MeV 1⁺, and 5.20 MeV 2^? excited states at the 34 MeV incident beam energy were analyzed and measured. The 62 MeV data of Goodman et al. were also reanalyzed. The direct one-step charge exchange caused by the spin-isospin dependent term in the two-body interaction can account well for the observed data. The strength of spin-isospin dependent effective interaction (gaussian form with a range parameter of 1.8 fm) was extracted to be 18.5 MeV.     

30MeV/u 40Ar+112,124Sn反应后角能谱温度的同位旋效应

在30MeV/u ⁴⁰Ar+^112,124Sn反应中用平行板雪崩计数器实现了前冲余核的测量.在不同的线性动量转移下用运动源模型拟合了后角的³He,α和⁶He能谱,发现³He的能谱斜率温度在¹²⁴Sn系统中高于¹¹²Sn系统,而⁶He的温度在¹¹²Sn系统中更高,α粒子在两个系统中没有明显差别.用热核粒子蒸发过程衰变道的选择性对这种同位旋相关性进行了解释.GEMINI的计算不能重现实验结果.     

Analyzing powers of the continuum spectra: 65 MeV polarized protons on 12C, 28Si, 45Sc, 58Ni, 93Nb, 165Ho, 166Er and 209Bi

Analyzing powers of the continuum spectra were measured for 65 MeV protons from ¹²C, ²⁸Si, ⁴⁵Sc, ⁵⁸Ni, ⁹³Nb, ¹⁶⁵Ho, ¹⁶⁶Er, ${}^{209}\text{Bi}\text{(}\text{p}\text{,}\text{p\#}\text{prime;}\text{X}\text{)}$ and ($\text{p}$, dX) reactions and from ⁹³Nb, ²⁰⁹Bi($\text{p}$, αX) reactions. The analyzing powers of the continuum spectra were found to be small at forward angles where the pre-equilibrium process is important. However they do not show a systematic tendency. This feature indicates the importance of the spin-dependent interaction as well as nuclear structure effects. On the other hand, the analyzing powers were very large and positive at backward angles where the shape of the energy spectra resembles that of an evaporation spectrum. The maximum values of the analyzing power in the backward hemisphere depend on the target mass for the A < 45 mass region and they are as large as 15%, 20% and 35% for ${}^{93}\text{Nb}\text{(}\text{p}\text{,}\text{p}\text{′}\text{X}\text{)}$, ($\text{p}$, dX), ($\text{p}$, αX) reactions at E_X = 20 MeV, respectively. These large values are mainly due to the entrance channel effect. There is no appreciable even-odd mass effect on the analyzing power for medium-mass nuclei. These features were unexpected from the conventional pre-equilibrium reaction models.     

27Al+27Al重离子耗散碰撞中能量自关联函数的分析

测量了²⁷Al+²⁷Al耗散反应产物的激发函数,束流²⁷Al⁸⁺的入射能量从114MeV到127MeV变化,能量步长为200keV.探测角度覆盖了实验室系10°—57°的连续区域.用不同的理论模型分析了耗散产物的能量自关联函数.结果表明,反应所形成的中间双核系统的阻尼相干转动造成了激发函数中不可平滑的涨落结构,相干转动的阻尼来自量子混沌运动.     

The sub-Coulomb 12C + 12C resonances in a microscopic 12C+12C,α+20Ne, 8Be+16O cluster basis

The low-J resonances in the Coulomb barrier region of the ¹² C+¹²C system are investigated in the framework of a microscopic cluster model basis including ¹²C+¹²C, α+ ²⁰Ne, and su8 Be+ ¹⁶O fragment decompositions. Calculations are carried out in an orthogonality condition model approximation in which Pauli-forbidden components are properly excluded from the basis but in which the interaction among cluster fragments is approximated by a local potential, obtained from a gaussian NN interaction by a folding procedure leading to both spherical and Q · Q terms. Only minor adjustments of overall strength and fall-off parameters are introduced to gain a consistent picture of the low-energy spectrum in the separate rearrangement channels. The basis includes cluster relative motion excitations with oscillator quanta from 12 to 20 and is not quite rich enough to give a detailed quantitative comparison between theory and experiment. Predicted excitation energies are too high by ~ 3 MeV and predicted ¹²C partial widths are too small to indicate a well-developed surface-peaked molecular character; but it does appear possible to identify a 5 MeV region as the potential seat of the 0⁺, 2⁺, 4⁺ resonances. The number and approximate spacing of the resonance fine structure components are in agreement with experiment.     

Decay of 48K, 49K and 50K

The ⁴⁸K, ⁴⁹K and ⁵⁰K nuclides have been produced in high energy fragmentation and analyzed by mass spectroscopy techniques. Their half-lives have been measured as 6 ± 1 s, 1.1 ± 0.3 s and and 0.7 ± 0.3 s, respectively. The γ-rays from their radioactive decay have been observed and the corresponding γ-intensities measured. The nuclide ⁵⁰K is shown to be a delayed neutron emitter. The antianalog states in the daughter Ca nuclei with a $\text{(1d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{)}{}^{\mathrm{?}}$ neutron configuration, preferentially populated in the β-decay, have been located. The corresponding $\text{1d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ neutron single-particle energy is found to remain approximately constant for these neutron-rich Ca isotopes.     

Recoil-distance lifetime measurements in 51Cr, 53Cr, 53Mn and 53Fe

Levels in ⁵¹Cr, ⁵³Cr, ⁵³Mn and ⁵³Fe were excited via (α, n) or (α, p) reactions. Using the recoil-distance method, mean-lives (in ps) have been obtained for excited states (keV) in the residual nuclei: ${}^{51}\text{Cr}\text{(2256) = 66±2,}{}^{53}\text{Cr}\text{(1536) = 21.5±3.5,}{}^{53}\text{Cr}\text{(2173) = 6.7±3.1,}{}^{53}\text{Mn}\text{(2564) = 20}{}^{\mathrm{+8}}{}_{\mathrm{?6}}\text{and}{}^{53}\text{Fe}\text{(1424) = 4.0±1.0}$. Reduced transition probabilities calculated from these values are compared with the available theoretical values.     

Scattering and reactions of 14C + 14C and 14C + 14C

We have studied elastic scattering, inelastic scattering and several transfer channels of the systems ¹⁴C + ¹⁴C and ¹⁴C + ¹²C over a wide range of energies up to E_c.m. = 35 eMeV and 32 MeV, respectively. The reaction channels were identified by means of kinematic coincidences between solid-state detectors, γγ coincidences were measured to determine cross sections for mutual inelastic scattering of ¹⁴C + ¹⁴C.Pronounced regular gross structures, similar to those found for ¹⁶O + ¹⁶O, are observed in the elastic excitation function of ¹⁴C + ¹⁴C at θ_c.m. = 90°, The angular distributions measured at the energies of the maxima and an optical-model analysis suggest that one or a few surface partial waves dominate the scattering behaviour. Correlated structure of narrower width is found in the inelastic channels and, to a lesser degree, in the transfer channels which appear with rather small cross sections.In ¹⁴C + ¹²C elastic scattering the gross structures are strongly fragmented, in contrast to ¹⁴C + ¹⁴C but similar to ¹²C + ¹²C. While the ¹²C(2⁺) excitation is very weak, the observed strengths of the ¹⁴C(3^?) excitation and of neutron transfer point to a substantial role of these channels as coupling partners to the elastic configuration and to their influence on the elastic scattering behaviour. A correlated intermediate structure is observed near 23.5 MeV, where a dominance of l = 18 is suggested by the elastic scattering angular distribution. This unexpectedly high l-value exceeds l_graz at this energy by at least two units of ?.