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.     

27Al+27Al耗散产物反应时间的提取

用发展了的Ericson统计理论,从²⁷Al+²⁷Al碰撞的耗散产物的激发函数提取了反应的相互作用时间约4.3×10^－21s.     

27Al+27Al耗散反应中间双核系统的核温度

从²⁷Al+²⁷Al耗散反应产物的激发函数中提取能量相干宽度Г,再求出双核系统的核温度T,并用相干转动的概念进行以合与解释.     

27Al+27Al耗散反应截面涨落的角度关联测量

在²⁷Al+²⁷Al(E_lab≈120MeV)耗散反应激发函数涨落的实验研究中,首次在较大的角度范围内获得截面涨落的角度关联系数和角度关联函数.实验结果表明,角度关联函数的形状呈现明显的非对称性,角度相干宽度至少为40°;截面涨落在前后角区表现出明显不同的角度相关性.     

19F+27Al耗散反应中双核系统的转动与形变

测量了¹⁹F+²⁷Al耗散反应产物B,C,N,O,F和Ne的激发函数,入射束流的能量从110.25MeV到118.75MeV, 能量步长为250keV. 从产物的 能量自关联函数中提取了反应中所形成的中间双核系统的转动惯量, 与相粘模型计算的刚体转动惯量相比较, 结果表明形成的双核系统有大的形变.     

80.9MeV 16O+27Al能量耗散和核子交换的关系

用带ΔE-E望远镜系统的飞行时间系统测量了80.9MeV ¹⁶O+²⁷Al反应出射产物的三重微分截面d³σ/dA dZ dE.对该反应中所出现的能量耗散和核子交换的关系进行了讨论.     

19F+45Sc深非弹反应产物的激发函数

测量了102MeV到108MeV ¹⁹F+⁴⁵Sc反应在θ₁=26°和θ₁=42°的耗散部分产物的激发函数,能量步长300keV,靶厚53μg/cm².用统计理论求得了各元素的能量相干宽度Γ,提取了反应的特征时间τ,探讨了耗散反应机制.     

19F+27Al耗散反应产物截面测量中的不重复性

在中国原子能科学研究院的HI-13串列静电加速器上完成了114MeV和118.75MeV的¹⁹F+²⁷Al耗散反应产物B, C, N, O, F, Ne, Na和Mg的微分截面测量. 条形²⁷Al同位素靶的大小尺寸为10mm×50mm, 平均 厚度约67μg/cm². 固定入射束流¹⁹F的能量, 通过移动靶位, 先后轰击了靶上20个不同的位置.实验结果表明, 在弹靶系统、入射能量以及探测系统都相同的多次独立的微分截面测量中, 截面的涨落不呈现高斯型几率分布. 截面测量的这种不重复现象难以用有限计数率的统计性质来解释.     

用动力学模型计算10.6MeV/u 84Kr(27Al,准裂变)反应的裂变时间

用单体耗散模型对10.6MeV/u ⁸⁴Kr在²⁷Al上引起的准裂变反应进行了计算,结果表明该准裂变反应的准裂变时间大于200×10^－22s.发现对本反应系统,准裂变的出现至少需要8MeV/u阈能.     

19F+27Al耗散反应中双核系统的转动与衰变

测量了¹⁹F+²⁷Al耗散反应产物B,C,N,O,F和Ne的激发函数, 入射束流的能量从110.25MeV到118.75MeV,能量步长为250keV. 用能量自关联函数方法从激发函数中提取了各反应产物的平均衰变宽度, 利用同时考虑反应中所形成的中间双核系统的转动特性和衰变特性而发展了的Ericson核反应统计理论, 讨论了¹⁹F+²⁷Al耗散反应中双核系统随时间的演化过程.     

Measurement of Excitation Function and Analysis of StatisticalProperty in 27Al+27Al mssipative Reaction

The angular distribuhon in the range of 0_cm=50°—90° and excitation funchon of the reachon products in heavy ion dissipahve reachon ²⁷Al+²⁷Al were measured, in the incident energy region from 114MeV to 120MeV with 200keV step. The statishcal property of the fluctuation of the excitation funchon in heavy ion dissipative reaction was discussed based on the integration of the macro outgoing channels.     

激发函数中的长程角度关联与量子态叠加

在较大的连续角区范围内测量了27Al+27Al耗散反应产物的激发函数,入射束流的能量从114MeV到127MeV,能量步长200keV.分析激发函数的角度关联,角度相干宽度超过40°,各个角度之间反应产物的互关联系数在0.6以上.用宏观条件下的量子态叠加讨论了这种长程角度关联.     

Study of the excitation functions of27Al(n, α)24Na,27Al(n,p)27Mg and28Si(n,p)28Al reactions

Cross sections for the reactions²⁷Al(n, p)²⁷Mg and²⁸Si(n,p)²⁸Al were measured by activation method between 13.40 and 14.83 MeV neutron energy. An accuracy of about 4% was achieved using the²⁷Al(n, α)²⁴Na reaction as a reference at 14.1 MeV where the relative excitation function has also been measured. Results obtained were compared to a recent compilation and that calculated by the Hauser-Feshbach model. Using the back-shifted level density formula and taking into account the contribution of the separated levels, the calculations were extended to the energy range from the threshold to 18 MeV. A structure was observed in the²⁷Al(n, α)²⁴Na reaction cross section curve around 14 MeV neutron energy.     

Messung von Wirkungsquerschnitten für die Reaktionen 27Al(N,P) 27Mg, 27Al(N, α)24Na und 27Al(N, α)24MNa im Energiebereich zwischen 6,3 MeV und 8,3 MeV

Measurements of Cross Sections for the Reactions ²⁷Al(N, P) ²⁷Mg, ²⁷Al(N, α)²⁴Na and ²⁷Al(N, α)^24mNa in the Energy Region between 6,3 MeV and 8,3 MeV Using the activation method cross-sections for the reactions ²⁷Al(n, α₀)²⁴Na, ²⁷Al(n, α₁)^24mNa and ²⁷Al(n, p)²⁷Mg have been measured in the energy range 6.3 MeV to 8.3 MeV. Fast neutrons were produced at the Stuttgart University 4 MV Dynamitron via the reaction ⁹Be(α, n)¹²C irradiating 0.52 μm beryllium layers on high pressure water-cooled copper backings. The energy of the He-ions was varied between 1.86 MeV and 2.76 MeV, while the average current was 200 μAmp. The neutron flux has been measured with a 2″ × 2″ NE 213 liquid scintillator cell.     

Comparison of one and two-neutron transfer near the coulomb barrier for the27Al(18O,16O)29Al,27Al(180,17O)28Al and27Al(13C,12C)28Al reactions

Total reaction cross sections for the transfer reactions²⁷Al(¹⁸O,¹⁶O)²⁹Al,²⁷Al(¹⁸O,¹⁷O)²⁸Al and²⁷Al(¹³C,¹²C)²⁸Al are reported for center-of-mass energies between 13 and 20 MeV for¹⁸O projectiles and between 11 and 17.5 MeV for¹³C projectiles. The reaction products,²⁹Al and²⁸Al, beta decay to²⁹Si and²⁸Si, respectively, and the subsequentγ decays of²⁹Si and²⁸Si were measured. Due to the relatively long beta decay half lives, data were taken in a beam-off mode, resulting in very clean spectra. Total cross sections were calculated and compared with a theoretical model for barrier penetration proposed by C.Y. Wong. Differences between¹⁸O induced one and two-neutron total transfer reaction cross sections are discussed.     

19F+27Al耗散反应产物激发函数的长程关联

在中国原子能科学研究院的HI 13串列静电加速器上完成了19F+27Al耗散反应产物的激发函数测量。 束流19F的入射能量从110.25 MeV到118.75 MeV, 步长250 keV, 测量了实验室系+57°, +31°, -15°和-29°出射的类弹产物B, C, N, O, F和Ne的激发函数。 观测到激发函数具有耗散反应的特征涨落结构, 分析了激发函数之间的长程角度关联以及强烈的电荷数关联。 Excitation functions have been measured for the projectile like fragments of B, C, N, O, F and Ne in the 27Al(19F,x)y reactions at incident energies from 110.25 MeV to 118.75 MeV in 250 keV steps. Strong cross section fluctuations in the excitation functions has been observed. The cross correlation coefficients of the excitation functions for different atomic number Z and for different scattering angle θ cm have been deduced. These coefficients are much larger than the statistical theoretical calculated ones. This indicates that there are strong correlations between different exit channels in the dissipative heavy ion collision of 27Al(19F, x)y.     

Properties of unbound high-spin states in27Al

Selectively excited high-spin states in²⁷Al have been located by the reaction¹²C(¹⁶O,p)²⁷Al. The excitation functions of these states have been measured at incident energiesE _cm=18.7 to 30.1 MeV at intervals of 150 keV. They exhibit maxima of presumably non-statistical origin. At four different energies the subsequent decay of the²⁷Al states has been studied by detecting the final heavy recoils with the Munich recoil spectrometer in coincidence with the proton emitted in the first stage of the reaction. Using this new method branching ratios of theγ-, α-, andn-decay have been measured. Based on angular correlation arguments spins up to 27/2? have been determined within the experimental accuracy of 1–2?. The observations suggest a superdeformed shape of²⁷Al at least in some of the states.     

Recoil properties of27Mg from the27Al(γ, π+)27Mg reaction

The mean ranges of the recoil nuclei from the reaction²⁷Al(γ, π⁺)²⁷Mg have been measured at maximum bremsstrahlung energies of 250, 400 and 800 MeV using catcher-foil techniques. The experimentally-determined ranges in directions along and perpendicular to the photon beam are in good agreement with calculated values based on the Fermi gas model and the impulse approximation.     

Absolute yield measurement of the reaction27Al(γ, 2pn)24Na

The reaction²⁷Al(γ, 2pn)²⁴Na is suitable as a secondary standard in high energy photonuclear studies. Thus, the absolute yields at bremsstrahlung maximum energies between 95 and 965 MeV have been measured.