对~(40)Ca9.5—10.5MeV能区内几组核能级宽度的测量

本文介绍了用γ共振吸收法测量~(40)Ca 9603.9keV,10321.0keV两组能级和9864.6,9868.8keV一组双重态能级的能级宽度,选用~(39)K(p,γ)反应所放出的γ射线激发相应的~(40)Ca吸收核能级。对于9603.9keV,10321.0keV的能级宽度,这里给出了比较精确的结果,相应的能级宽度分别为T=188±47eV,T=91±15eV。对于9864.6,9868.8keV能级,结果为T=100±24eV,T=899±214eV,由于~(40)Ca 9864.6,9868.8keV两能级靠得很近,因此这里用γ共振吸收法测量它们的能级宽度与以往有所不同,将同时有两组γ射线用来激发同样两个能级而发生交叉激发。我们对相应的实验处理方法作了推广。此外,用(p,γ)共振产额法测量了~(40)Ca 9603.9keV,10321.0keV能级宽度,得到了与γ共振吸收法一致的结果。本文还对~(40)Ca 9603.9keV,10321.0keV能级的(p,γ)共振强度S_(pγ)、同位旋T等进行了讨论。     

用阻塞效应测量28Si 13.095MeV激发态能级寿命

改进Al单晶样品的处理方法,得到了高质量的样品。进行了Al单晶辐照损伤实验,直接测量了E_p=1565keV时²⁷Al(p,α)²⁴Mg共振所形成的²⁸Si 13.095MeV激发态能级寿命。采用MonteCarlo模拟和“分析”方法计算得到其寿命值τ=16.3±2.4as,对应的能级宽度Γ=40±6eV,与文献报道的共振产额法结果符合得较好。 关键词：     

用阻塞效应测量~28Si 13.095MeV激发态能级寿命

改进Al单晶样品的处理方法,得到了高质量的样品。进行了Al单晶辐照损伤实验,直接测量了E_p=1565keV时~(27)Al(p,α)~(24)Mg共振所形成的~(28)Si13.095MeV激发态能级寿命。采用Monte Carlo模拟和“分析”方法计算得到其寿命值τ=16.3±2.4as,对应的能级宽度Γ=40±6eV,与文献报道的共振产额法结果符合得较好。     

24Mg核11.528MeV能级的验证

本文介绍用γ共振吸收法检验²⁴Mg核11.528MeV能级的实验结果。实验中在此能级的附近能区意外地发现多个精细能级,数据分析给出这些能级的能量E_r和宽度Г_a等数据,同时还获得了与以往数据不同的发射能级宽度Г_e。 关键词：     

应用共振吸收谱仪测量Al对γ射线的衰减系数

应用穆斯堡尔谱仪测量了AI对⁵⁷Fe^*核14.4keV的γ射线的衰减系数μ,两组测量值的平均结果为μ=(0.00874±0.00020)cm²/mg。 关键词：     

正电子在铝中湮没γ射线能量的精密测量

用Ge(Li)探测器测量正电子在两种不同来源的铝样品中的湮没辐射,以¹⁸¹Hf的482keVγ,峰做为基准,重复测定湮没峰与基准峰的相对位置,精密度达到±6eV。结果表明,在两种铝样品中的电子静止质量在10eV水平上是一致的。 关键词：     

平面阻塞效应测量Ep=1565keV时27Al(p,α)24Mg共振反应寿命

采用(111)面阻塞效应测量了E_p=1565keV共振时²⁷Al(p,α)²⁴Mg核反应寿命。用解析方法分析实验数据。测到的核寿命τ=17.9_-4.0^+4.4as,与<110>轴阻塞效应测量结果和文献给出的结果在误差范围内一致。测量了E_p=1183.4keV时(111)面的α粒子的阻塞分布,并与理论计算作了比较。 关键词：     

22Na(p,γ)23Mg反应的实验研究

讨论了目前有关22Na(p,γ)23Mg反应的实验研究工作,结合兰州放射性束流线上的放射性束流23Al的β+延发质子衰变实验的测量结果,给出了23Al延发衰变的质子能谱,并比较了近期实验给出的相关能级的自旋、宇称值,正是由于这种自旋、宇称和能级部分宽度的不确定性,导致了反应率计算的不确定性. 计算了同位旋相似态的共振强度. 对于测量到的新的延发衰变能级Ed=8.916MeV,由于没有相应的能级宽度值,实验仅给出其相对共振强度值.     

核子-核子碰撞截面对同位素标度参数α的介质效应

核子能量在40—60MeV能区范围,对在两对重离子中心碰撞系统⁴⁰Ca+⁴⁸Ca和⁶⁰Ca+⁴⁸Ca以及¹¹²Sn+¹¹²Sn和¹²⁴Sn+¹²⁴Sn 的反应中就同位素标度参数α对于核子-核子碰撞截面σ^med_NN(α_m)的介质 关键词： 同位素标度行为 介质效应 核子-核子碰撞截面 重离子碰撞     

核子-核子碰撞截面对同位素标度参数α的同位旋效应

对两对重离子中心碰撞系统⁴⁰C+⁴⁰Ca 和⁶⁰Ca+⁴⁰Ca以及¹¹²Sn+¹¹²Sn和¹²⁴Sn+¹²⁴Sn反应中就同位素标度参数α对于核子-核子碰撞截面的同位旋效应进行了研究.计算结果表明α对同位旋相关核子-核子碰撞截面σ^med_{NN关键词： 同位旋效应 核子-核子截面 机理 同位素标度}     

The Jπ = 3− doublet at Ex = 6241 keV in 18F: Isospin mixing

The resonance previously observed at E_x = 6241 keV in the reactions ¹⁷O(p, γ)¹⁸F and ¹⁴N(α, γ)¹⁸F has been found to be a closely separated doublet (ΔE_x = 2.09±0.04 keV). Resonance strengths in ¹⁷O(p, γ)¹⁸F, ¹⁷O(p, α)¹⁴N and ¹⁴N(α, γ)¹⁸ have been measured and partial widths for the resonance states have been obtained. The doublet was further investigated by means of the ⁴He(¹⁴N, α)¹⁴N reaction using the differentially pumped gas target at CRNL. Analysis of these data using R-matrix theory yielded J^π = 3^? for both states and more precise values of the α-particle widths (Γ_α(lower) = 133 ±4 eV; Γ_α(upper) = 137 ±4 eV). The reduced α-particle widths and the E1 and M1 transition strengths indicate that the doublet arises from the nearly complete mixing of T = 0 and T = 1 eigenstates which in the absence of an isospin breaking interaction would have been separated by less than 40 eV. The α-particle scattering experiments included the J^π = 1⁺ resonance at E_x = 6257 keV and yielded the new values of Γ_α = 580±12 eV and Γ_p = 25⁺³⁵_?25 eV.     

The ground stateM1 strength in40Ca

The M1 gamma decay strengths of the ground state transitions of the 1⁺,T=1 states of⁴⁰Ca at 9.86 MeV and 10.32 MeV have been measured using the reaction³⁹K(p,γ)⁴⁰Ca. The measured ground state gamma decay widths of these levels are 1.06±0.15 eV and 5.8±0.8 eV respectively. These relatively large M1 strengths can be explained by a shell model calculation incorporating excited core configurations.     

A study of the excited states of23Na from the22Ne(p, γ)23Na reaction

The gamma decays of 19²²Ne(p, γ)²³Na resonances in the range ofE _p =400?1300 keV have been investigated by means of a 38 cm³ Ge(Li) detector. Branching ratios of the resonances and bound states were determined. Gamma-ray energy measurements yield the energies of 19 bound states and the value of 8794.0±1.5 keV forQ. The existence of the 3913 keV doublet state was studied through the (p, γ) reaction. No evidence for such a doublet was found.     

A new determination of the partial widths of the 16.11 MeV state in 12C

The partial widths of the second T = 1 state of ¹²C, at 16.11 MeV excitation energy, have been determined by measuring the ¹¹B(p, γ) and ¹¹B(p, α) cross sections at the E_p = 163 keV resonance corresponding to this state. These measurements result in the new values of Γ_p = 21.7 ± 1.8 eV and Γ_γ = 21.6 ± 3.3 eV, for the partial widths of this state; approximately 3 times smaller and larger, respectively, than the present values in the literature. The new result for the proton width eliminates a serious discrepancy found in an earlier comparison of the partial widths of the T = 1 analogue states of the A = 12 system. Measurements were also made of the ¹¹B(d, n)¹²C¹ reaction to compare the proton widths of the 15.11 and 16.11 MeV T = 1 states; these measurements confirm the new, smaller proton width for the 16.11 MeV state. An attempt was also made to determine the γ-width of the 16.11 MeV state by measuring the γ-branching ratio in the ¹⁰B(³He, p)¹²C¹(γ)¹²C reaction.     

Resonance neutron capture in 52Cr

Neutron capture γ-ray measurements have been performed upon a natural sample of Cr. Twenty-six γ-rays were observed from the 1626 eV resonance of the ⁵²Cr(n, γ)⁵³Cr reaction, and twenty-four of them were assigned to a level scheme. A value of $\text{3}\text{2}$^? was determined for the spin-parity of this resonance. The neutron separation energy, derived from a separate thermal measurement with an enriched (99.9 %) ⁵²Cr sample was determined to be 7939.1 ± 0.2 keV. The high (n, γ) (d, p) correlation found for thermal capture is absent for the p-resonance, however the γ-ray intensities from thermal and resonance capture are correlated, with r = 0.86_?0.11^+0.06.     

Resonant neutron capture in 40Ca

The neutron capture cross section of ⁴⁰Ca has been measured with ≈ 0.2 % energy resolution below E_n = 300 keV. Resonance parameters have been extracted for many new p- and d-wave resonances. Gamma-ray spectra were also measured following capture in one doublet and two resolved resonances below 50 keV. Strong feeding of low-lying p-wave levels was observed in all cases. Calculations showed that valence transitions were inadequate to account for the observed dominance of these transitions and a further mechanism is required. The average resonance parameters obtained from the data are as follows: 〈D〉 = 37 + 4keV, 10⁴S₁ = 0.16 ± 0.05, 10⁴S₂ = 2.0 ± 0.7. The average radiative widths and standard deviations of their distributions were found to be strongly l-dependent as follows: 〈Γ_γ〉_s = 1.5 ± 0.9 eV, 〈Γ_γ〉_p = 0.36 ± 0.09 eV and 〈Γ_γ〉_d = 0.7 ± 0.4 eV.     

Investigation of dual decay of70Ga (21 min)

The weakβ ^?-branchings in⁷⁰Ga decay leading to excited states in⁷⁰Ge at 1039 keV, and 1215 keV were measured byβ ^?-ray and γ-ray detection in 4π geometry to be 0.36 ±0.02%, and 0.32±0.01%, respectively. The weak electron capture decay of⁷⁰Ga was confirmed and its intensity measured to be 0.41±0.05%. The energy of the γ-rays was remeasured to be 176.17±0.02 keV, and 1039.20±0.08 keV.     

Proton induced resonances on 21Ne

Excitation curves for the ${}^{21}\text{Ne}\text{(}\text{p}\text{, γ)}{}^{22}\text{Na}\text{,}{}^{21}\text{Ne}\text{(}\text{p, p}\text{′γ)}{}^{21}\text{Ne and}{}^{21}\text{Ne}\text{(}\text{p, p}\text{)}{}^{21}\text{Ne}$ reactions have been obtained for E_p = 0.4–1.6 MeV. Neon gas enriched to 92 % in ²¹Ne was recirculated in a differentially pumped gas target system. The fifteen previously reported (p, γ) resonances were established and nineteen new (p, γ) resonances found. Anomalies in the elastic scattering yield were observed for fourteen resonances. The reported state at E_x = 7278 ± 7 keV in ²²Na was resolved into a doublet separated by 1 keV. All unbound states in ²²Na, observed previously in other reactions, have been confirmed as resonance states in the energy range covered, with the exception of the E_x = 7942 ± 7 keV state. The new E_p = 663, 694, 1235, 1432 and 1543 keV resonances correspond to new unbound states in ²²Na. Excitation energies, γ-ray decay schemes, resonance widths and strengths as well as limits on J^π assignments are reported for all the resonances. From the Coulomb excitation of the E_x = 350 keV, first excited state in ²¹Ne a value of B(E2) = 0.014 ± 0.002 e² · b² is deduced. The astrophysical as well as the nuclear structure implications of the present results are discussed.     

Q-value of the 40Ca(α, γ)44Ti reaction

The Q-value of the ⁴⁰Ca(α, γ)⁴⁴Ti reaction has been measured by comparing resonance α-particle and γ-ray energies to those of the prominent $\text{T =}\text{3}\text{2}$ resonance in the ¹⁵N(α, γ)¹⁹F reaction, for which the Q-value is known with an accuracy of 0.12 keV. The result for the ⁴⁰Ca(α, γ)⁴⁴Ti reaction is Q = 5127.1 ± 0.7 keV. It follows that the mass excess of ⁴⁴Ti is ?37549 ± 1 keV.     

Measurement of partial radiation widths of high energy transitions from keV capture resonances in56Fe and58,60Ni

High energyγ-ray transitions to low-lying states following neutron capture in⁵⁶Fe and^58,60Ni have been investigated for individual resonances in the neutron energy range 7–70keV using a 50cc Ge(Li)-detector. Partial radiation widths fors- and 1>0 wave resonances were determined. For the 1>0 wave resonance in⁵⁸Ni at 47.8 keV a spin of 3/2 was derived. Theγ-ray strength forM1 transitions was found to be (21±17)×10^?9 and (16±7)×10^?9MeV^?3 for⁵⁶Fe and⁵⁸Ni, respectively. The partial radiation widths of the studieds-wave resonances were compared with valence model calculations.