20Na的β+延发α粒子测量

利用兰州放射性次级束流线提供的²⁰Na束流,通过²⁰Naβ^{+ 20}Ne→¹⁶O+α过程,测量了²⁰Na的衰变半衰期T_1/2及衰变α粒子能谱.结果表明,除了E_d≥2.688MeV的9条较高激发能级的衰变α粒子外,实验中还观察到衰变能量E_d为0.890和1.054MeV,1.991MeV,2.424和2.457MeV的²⁰Ne低激发能级的3条α谱线.     

RIBLL上的β+缓发粒子发射的在束测量

报道了在新建成的放射性次级束流线上完成的²⁰Na的β+缓发α粒子发射²⁰Na—→β^+　20Ne→¹⁶O+α的在束测量.通过飞行时间和能损符合的方法实现²⁰Na次级束流的在束鉴别与调制.在束和停束两个获取时段分别完成对次级束流和β+缓发粒子的记录.利用脉冲发生器和记数器实现²⁰Na缓发粒子衰变半衰期的测量.实验测量到²⁰Ne几个低能共振能级的衰变能量分别为2.69,3.09,4.74,5.54MeV,相对强度分别为100,4.15,1.10,15.20.测量到²⁰Na的β⁺缓发α衰变的半衰期为(459±7)ms,与现有的核数据基本上吻合.     

23Al的β+延发质子测量

利用ＴＯＦ－ Ｅ和０°注入探测器的方法,鉴别并测量了２３Ａｌβ＋延发质子衰变能谱,通过精密脉冲发生器和计数器测得２３Ａｌ的半衰期 Ｔ１／２＝（４７６±４５）ｍｓ．实验中重现了能量为０．２１６,０．２７８,０．４３８,０．４７９ＭｅＶ的低能衰变质子．另外,还观察到了一个新的β＋延发衰变能级 Ｅｘ＝ ８．９１６ＭｅＶ,并给出了它们的相对强度．     

缺中子176Ir核β+/EC衰变研究

在210MeV的束流能量下, 利用重离子熔合蒸发反应¹⁴⁶Nd(³⁵Cl, 5nγ)¹⁷⁶Ir产生具有β⁺/EC衰变性质的核素¹⁷⁶Ir,由氦喷嘴快速带传输系统将反应产物传送到低本底区进行测量. 经过实验数据的离线处理分析,对早先发表的¹⁷⁶Ir衰变γ跃迁进行确认的同时又发现了3个新能级和10条新的γ射线, 丰富了¹⁷⁶Os核的低位激发态能级纲图. 并根据典型γ射线的衰变时间谱建议了¹⁷⁶Ir核的一个长寿命的低自旋同核异能态.     

Ir β+/EC衰变及其系统性分析

在在束实验条件下用γ-γ符合方法研究了具有β⁺/EC衰变性质的核素^176,178Ir的衰变γ射线. 另外借助氦喷嘴快速带传输系统在排除在束干扰的条件下, 进一步对¹⁷⁶Ir的β⁺/EC衰变进行了研究, 在确认在束测量新γ射线的同时建议了¹⁷⁶Ir的一个低自旋同核异能态. 从衰变系统性方面对^176,178Ir核中存在同核异能态的合理性和可能性进行了分析.     

130Nd和140Tb的EC/β+衰变研究

利用能量为170MeV左右的³⁶Ar重离子束轰击⁹⁶Ru和¹⁰⁶Cd浓缩同位素靶,分别生成缺中子同位素¹³⁰Nd和¹⁴⁰Tb.借助氦喷嘴带传输系统,用X–γ和γ–γ符合方法,分离鉴别了这两种核素,并进一步测定了它们的衰变性质.得到¹³⁰Nd的半衰期为(13±3)s,首次建议了它的EC/β+衰变纲图,推测了其子核¹³⁰Pr的基态和低位能级的自旋宇称.修订了¹⁴⁰Tb的原有极简单的EC/β⁺衰变纲图并指认¹⁴⁰Tb的基态自旋宇称为7⁺.     

缺中子130Pm和128Pr核的EC/β+衰变研究

171MeV³⁶Ar束轰击⁹⁶Ru靶由熔合蒸发反应生成了¹³⁰Pm和¹²⁸Pr核.由氦喷嘴快速带传输系统将反应产物送到低本底区.基于X-γ-t,γ-γ-t符合测量,首次建立了¹³⁰Pm的(EC+β⁺)衰变纲图.重新研究了¹²⁸Pr核的衰变,订正和补充了γ射线,建立了新的(EC+β⁺)衰变纲图.     

缺中子120Ba核EC/β+衰变的再研究

利用171MeV ³²S束轰击⁹²Mo靶,熔合蒸发(2n2p)反应合成了¹²⁰Ba核.由氦喷嘴反冲快速带传输系统将反应产物送到低本底区.位于带子两侧的两个平面型高纯锗探测器对反应产物进行了符合测量.经离线数据分析,对早先发表的¹²⁰Ba衰变γ射线予以确认,并补充了19条强度较弱、能量较低的γ射线.建议了¹²⁰Ba的衰变纲图共包括35条γ射线和25条能级.     

ψ′→J/ψ π+π－衰变振幅的分波分析

从ψ′→J/ψ π⁺π^－衰变振幅的普遍表达式和过程的运动学出发,给出了ππ不变质量谱,角关联谱和不变质量–角关联双变量谱;进行了分波分析,使得从实验上检测D波跃迁成为可能.文中还对来自J/ψ反冲的D波跃迁作了讨论.     

高能核碰撞中的K+/π+比与次级碰撞效应

用程函近似分析在高能核碰撞中次级作用对K⁺/π⁺比的影响.计算表明,在K⁺/π⁺比中次级碰撞效应是重要的.     

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.     

Proton threshold states in 26Al

The energy levels of ²⁶Al between E_x = 6.3 and 6.5 MeV, corresponding to proton threshold energies in the ²⁵Mg + p reaction from $\text{E}{}_{\mathrm{<mtext>p</mtext>}}\text{= 0}\text{to}\text{200}\text{keV}\text{, have been investigated using the reactions}{}^{27}\text{Al(su3}$He, α)²⁶Al and ²⁴Mg(³He, p)²⁶Al. Despite early work reporting a doublet at E_x = 6346 keV and E_x = 6362 keV, most subsequent work reported a single state with conflicting spin and parity assignments. Our work clearly establishes the presence of the doublet and resolves the conflicts. We find that there are six states in this excitation energy region, including a new state at E_x = 6410 ± 5 keV. The l-values leading to possible spin and parity assignments for all these states have been made using DWBA. We conclude however that only three of these six states may contribute to the production of ²⁶Al by the ²⁵Mg(p, γ) reaction in the MgAl cycle and the new structure of ²⁶Al reported here can substantially increase the production rate of ²⁶Al in stellar reactions.     

Beta decays of 25Na, 25Al and 29Al

The radioactivities ²⁵Na, ²⁵Al, and ²⁹Al were produced in the ²³Na(t, p)²⁵Na, ²⁴Mg(d, n)²⁵Al, and ²⁷Al(t, p)²⁹Al reactions using a 3.5 MV Van de Graaff. γ-radiations were measured by means of a target-transfer system and a Ge(Li) detector with or without Compton suppression. Decay schemes derived for ²⁵Na and ²⁹Al are in general agreement with earlier results, but with improved accuracy of branching ratios and much sharper limits on the intensities of certain unobserved β- and γ-ray transitions. Precision measurements of the energies of principal γ-rays gave results in keV for the listed decaying bodies as follows: ²⁵Na ? 1611.716(11); ²⁵Al ? 1611.708(11); and ²⁹Al ? 1273.361(9). The energy determinations of the ²⁵Mg 1612 keV γ-transition measured in the decays of ²⁵Na and ²⁵Al differ by 8 ± 9 eV.     

Decay amplitudes of the 208Pb(0+) analogue resonance

Measurements were made of elastic and inelastic proton scattering on ²⁰⁷Pb targets in the energy range from 11.1 to 14.4 MeV. The scattering to the $\text{1}\text{2}{}^{\mathrm{?}}$ ground state and to the $\text{3}\text{2}{}^{\mathrm{?}}$ and $\text{5}\text{2}{}^{\mathrm{?}}$ exciced levels was analyzed in terms of a 0⁺ analogue resonance interfering with the non-resonant background and with the contribution from the 3^? resonance. The resonance parameters were determined together with the magnitude and relative sign of three background components.     

Désintégration β− de 30Al

Gamma rays following the β^? decay of ³⁰Al have been investigated with a Ge(Li) detector. The ³⁰A1 sources were produced by fast neutron bombardment of an enriched ³⁰Si sample. Evidence for two previously unreported β^? branches has been deduced. The existence of allowed β^? transitions to J^π = 2⁺and 3⁺ states and to the J^π = 4⁺ level at 5.95 MeV determines $\text{J}{}^{\mathrm{\pi }}\text{= 3}{}^{\mathrm{+}}$ for the ³⁰Al ground state $\text{(T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{= 3.56 ± 0.02 s)}$. These results are compared to a recent shell-model calculation.     

Proton yields from quasielastic pion scattering on 27Al and 208Pb

A singles measurement of the quasielastic scattering of 255 MeV pions by ²⁷Al and ²⁰⁸Pb has been made. The measured values for the ratio R of π⁺ and π^? induced cross section, averaged over all measured angles of 2.2 ± 0.2 and 1.5 ± 0.1 for ²⁷Al and ²⁰⁸Pb respectively are substantially below the classical impulse approximation value of 11. A semiclassical nucleon charge exchange model is described for singles and coincidence measurements and is compared with the measured proton spectra. The comparison indicates that the singles proton spectra are dominated by events other than the quasielastic process whereas the coincidence data reported earlier and compared with the present calculations support the quasielastic interpretation. A strongly decreasing dependence of R on A for coincidence measurements may be interpreted as supporting the view that recoil nucleon charge exchange plays an important role in the quasielastic knockout process.     

Incomplete fusion of the 16O + 27Al reaction

Velocity spectra of fusion-like residues produced in the reactions of 90 MeV and 150 MeV ¹⁶O with ²⁷Al were measured. At 90 MeV the velocity spectra were well reproduced by a statistical model calculation. At 150 MeV the observed centroids of the velocity spectra deviate from the statistical model predictions. The centroid shifts as a function of the atomic and mass numbers of evaporation residues were analyzed by two different model calculations based on the assumption that incomplete fusion is (a) a peripheral process, or (b) independent on the angular momentum of the entrance channel, respectively. The later assumption is in better agreement with the presented data.     

70As(β++EC)衰变到70Ge的低自旋激发态(英文)

通过70As的放射性衰变研究了70Ge的激发态,新发现能量为1 036.99,1 196.66,1 539.29和2 531.7 keV的四条新γ射线,重新确认了2 219.34 keV γ射线的跃迁位置,新确认496.74,1 295.24和1 417.24 keV这三条γ射线首次放入衰变纲图,本工作证实了1 881.67,2 325.42和2 424.41 keV γ射线的跃迁位置,建议了能量为4 243.10和5 265.81 keV的两个新能级,建立了新的衰变纲图,基于比较半衰期和γ跃迁分支比建议了一些能级的自旋-宇称。The excited states of the 70Ge nucleus are investigated in radioactive decay of the 70As. Four new transitions with 1 036.99, 1 196.66, 1 539.29 and 2 531.7 keV are found for the first time. The position of 2 219.34 keV transition are reassigned, the transition positions of 496.74, 1 295.24 and 1 417.24 keV γ-rays are assigned for the first time, and the placements of 1 881.67, 2 325.42 and 2 424.41 keV γ-rays are confirmed in the present work. Two new levels, at 4 243.10 and 5 265.81 keV excitation energy, respectively, are proposed. The decay scheme is established and for a number of levels spin-parity assignments are suggested on the basis of logft values and γ-branching ratios.     

The 1Σ+-X1Σ+ transition of the PN molecule

The recently observed ¹Σ⁺-X¹Σ⁺ transition of the PN molecule (J. Phys. B.13, 2251–2254 (1980)) has been photographed at high dispersion in the 1600–1900-Å region. A rotational analysis is carried out and shows 11 vibrational levels of the new ¹Σ⁺ state. These levels are perturbed and absolute vibrational numbering cannot be determined. Some perturbations can be accounted for by interactions with the A¹Π state. Weakening of lines are explained as accidental predissociations and allow us to discuss the dissociation energies of the X¹Σ⁺ and A¹Π states.     

Re-evaluation of the ^23Mg（p,γ） ^24Al reaction rate

Based on a new screening Coulomb model, this paper discusses the effect of electron screening on proton capture reaction of 23Mg. The derived result shows that, in some considerable range of stellar temperatures, the effect of electron screening on resonant reaction is prominent; on the non-resonant reaction the effect is obvious only in the low stellar temperatures. The reaction rates of ^23Mg（p,γ） ^24Al would increase 15%-25% due to the fact that the electron screening are considered in typical temperature range of massive mass white dwarfs, and the results undoubtedly affect the nucleosynthesis of some heavier nuclei in massive mass white dwarfs.