~(22)Na(p,γ)~(23)Mg反应的实验研究

讨论了目前有关2 2 Na(p ,γ) 2 3Mg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2 3Al的β+延发质子衰变实验的测量结果 ,给出了2 3Al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 =8.91 6MeV ,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

利用离子注入~(15)N靶研究超低能区~(15)N(p,α)~(12)C核反应

描述了利用离子注入固体靶测量15N(p ,α) 12 C核反应微分截面的实验过程和方法 ,给出了在163keV≤Ec≤ 360keV能区 90°方向上的微分截面测量结果和激发函数曲线 ,并对该反应的基本特征进行了分析和描述。

高能Ar~+辐照P型CdZnTe的电学特性和光致发光

采用能量 2 Ge V、剂量 10 1 0— 10 1 3cm- 2的 Ar+辐照 P型 Cd0 .96 Zn0 .0 4Te材料 ,对辐照前后和不同辐照剂量的样品进行了电学测试和光致发光研究 .实验结果和分析表明 ,Ar+ 辐照在 Cd0 .96 Zn0 .0 4Te中产生了更大密度的受主型缺陷和散射中心 ,引起材料载流子 (空穴 )浓度的增大和迁移率的降低 .随着辐照剂量的增大 ,载流子迁移率的降低要比载流子浓度增大得快 ,导致材料电阻随辐照剂量增大而增大

质子滴线区新核素~(25)P的鉴别

在兰州放射性束流装置 RIBLL上 ,利用磁刚度 Bρ、飞行时间 t TOF和多重望远镜ΔE- E联合探测方法测量了 69Me V/u36Ar轰击 Be靶产生的 P同位素碎片的同位素分布 ,并与 EPAX经验公式的计算结果进行了比较 ,在质子滴线区首次鉴别出了新核素 2 5P.

50MeV/u~(20)Na+~(208)Pb→p+~(19)Ne+~(208)Pb反应的探测效率模拟

用半经典模型考虑20Ｎａ＋２０８Ｐｂ→ｐ＋１９Ｎｅ＋２０８Ｐｂ的Ｃｏｕｌｏｍｂ解离过程。用ＭｏｎｔｅＣａｒｌｏ方法计算前角放置的望远镜阵列对Ｃｏｕｌｏｍｂ解离碎片的探测效率。讨论了天体环境下ｐ＋１９Ｎｅ→２０Ｎａ俘获反应道的低能级共振截面测量的可行性。

Combined study of gamma p ->eta p and pi(-)p ->eta n in a chiral constituent quark approach

Within a chiral constituent quark model approach, η-meson production on the proton via electromagnetic and hadron probes is studied. With few parameters, the differential cross section and polarized beam asymmetry for γp → ηp and differential cross section for π − p → ηn processes are calculated and successfully compared with the data in the center-of-mass energy range from threshold up to 2 GeV. The five known resonances S11(1535), S11(1650), P13(1720),D13(1520), and F15(1680) are found to be dominant in the reaction mechanisms in both channels. Possible roles played by new resonances are also investigated; and in the photoproduction channel, significant contribution from S11 and D15 resonances, with masses around 1715 and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of N ∗ → πN, ηN are also presented and found to be consistent with the Particle Data Group values.

Measurement of the inelastic branch of the O-14(alpha, p)F-17 reaction: Implications for explosive burning in novae and x-ray bursters

A measurement of the inelastic component of the key astrophysical resonance in the 14O(α,p)17F reaction for burning and breakout from hot carbon-nitrogen-oxygen (CNO) cycles is reported. The inelastic component is found to be comparable to the ground-state branch and will enhance the 14O(α,p)17F reaction rate. The current results for the reaction rate confirm that the 14O(α,p)17F reaction is unlikely to contribute substantially to burning and breakout from the CNO cycles under novae conditions. The reaction can, however, contribute strongly to the breakout from the hot CNO cycles under the more extreme conditions found in x-ray bursters.

Proposal for studying N* resonances with the (p)over-barp -> (p)over-barn pi(+) reaction

A theoretical study of the (p) over barp -> (p) over barn pi(+) reaction for antiproton beam energy from 1 to 4 GeV is made by including contributions from various known N* and Delta* resonances. It is found that for the beam energy around 1.5 GeV, the contribution of the Roper resonance N-(1440)* produced by the t-channel sigma exchange dominates over all other contributions. Since such a reaction can be studied in the forthcoming PANDA experiment at the GSI Facility of Antiproton and Ion Research (FAIR), the reaction will be realistically the cleanest place for studying the properties of the Roper resonance and the best place for looking for other "missing" N* resonances with large coupling to N sigma.

Investigation of excited states in Mg-22 via resonant elastic scattering of Na-21+p and its astrophysical implications

The excited states in 22Mg have been investigated by the resonant elastic scattering of 21Na + p. A 4.0 MeV/nucleon 21Na beam was separated by the Center for Nuclear Study (CNS) radioactive ion beam separator (CRIB) and then used to bombard a thick (CH2)n target. The energy spectra of recoiled protons were measured at scattering angles of θc.m. ≈ 172◦ , 146◦, and 134◦, respectively. A wide energy-range of excitation function in 22Mg (up to Ex ∼ 8.9 MeV) was obtained simultaneously with a thick-target method, and a state at 7.06 MeV was newly observed. The resonant parameters were deduced from an R-matrix analysis of the center-of-mass (c.m.) differential cross-section data with a SAMMY-M6-BETA code. The astrophysical resonant reaction rate for the 18Ne(α,p)21Na reactionwas recalculated based on the present parameters. Generally speaking, the present rates are much smaller than the previous ones.

Theoretical study of p-d hybridization in Co perovskite

The real-space recursion method and unrestricted Hartree-Fock approximation have been applied to calculate the density of states of various Co perovskite, CeCoO3, SrCoO3 and Sr1-xCexCoO3. We have studied the magnetically ordered states of these Co perovskites in an enlarged double cell, and find its various magnetic structures due to the occupancy of 3d band and its interaction with neighboring Co ions. In this study, we have studied the p-d hybridization of the three Co perovskites, we find t(2g) electrons are localized and the flat e(g) band is responsible for the itinerant behavior, and although the rare earth elements itself contribute little to the DOS at the Fermi energy, the DOS at Fermi energy and the magnetic moment changed consequently because of different valence of Co ions in these compounds and p-d hybridization effect is very important. (C) 2009 Elsevier B.V. All rights reserved.

Hyperfine quenching of the 3s3p P-3(0) level in Mg-like ions

Hyperfine quenching rates of the 3s3p P-3(0) level in Mg-like ions were calculated using the GRASP2K package based on the multi-configuration Dirac-Hartree-Fock method. Valence and core-valence correlation effects were accounted for in a systematic way. Breit interactions and QED effects were included in the subsequent relativistic CI calculations. Calculated rates were compared with other theoretical values and with experiment, and a good agreement with the latest experimental value for the Al-27(+) ion (Rosenband et al 2007 Phys. Rev. Lett. 98 220801) was found. Furthermore, we showed in detail the contributions from Breit interaction and QED effects to concerned physical properties. Finally, electronic data were presented in terms of a general scaling law in Z that, given isotopic nuclear spin and magnetic moment, allows hyperfine-induced decay rates to be estimated for any isotope along the isoelectronic sequence.

Doubly excited 2s2p P-1,3(1) resonances in photoionization of helium

The multi-configuration Dirac Fock (MCDF) method is implemented to study doubly excited 2s2p P-1,3(1) resonances of the helium atom and the interference between photoionization and photo excitation autoionization processes. In order to reproduce the total photoionization sprectra, the excited energies from the ground 1s(2) S-1(0) state to the doubly excited 2s2p P-1,3(1) states and the relevant Auger decay rates and widths are calculated in detail. Further more, the interference profile determined by the so-called Fano parameters q and rho(2) is also reproduced. Good agreement is found between the present results and other available theoretical and experimental results. This indeed shows a promising way to investigate the Fano resonances in photoionization of atoms within the MCDF scheme, although there are some discrepancies in the present calculations of the 2s2p P-3(1) state.

Isospin dependence of nucleon (PF2)-P-3 superfluidity in asymmetric nuclear matter

We have investigated the isospin dependence of the neutron and proton (PF2)-P-3 superfluidity in isospin-asymmetric nuclear matter within the framework of the Brueckner-Hartree-Fock approach and the BCS theory. We show that the (PF2)-P-3 neutron and proton pairing gaps depend sensitively on isospin asymmetry of asymmetric nuclear matter. As the isospin asymmetry increases, the neutron (PF2)-P-3 superfluidity becomes stronger and the peak value of the neutron (PF2)-P-3 pairing gap increases rapidly. The isospin dependence of the proton (PF2)-P-3 superfluidity is shown to be opposite to the neutron one. The proton (PF2)-P-3 superfluidity becomes weaker at a higher asymmetry and it even vanishes at high enough asymmetries. At high asymmetries, the neutron (PF2)-P-3 superfluidity turns out to be much stronger than the proton one, implying that the neutron (PF2)-P-3 superfluidity is dominated in the highly asymmetric dense interior of neutron stars.

Entrance-channel dependence of isospin effects on double n/p ratio in HIC

Within the hadronic transport model IBUU04, we investigate the effect of density-dependent symmetry energy on double neutron/proton (n/p) ratio of free nucleons in heavy ion collisions by taking four isotopic Sn+Sn reaction systems. Especially the entrance-channel asymmetry and impact-parameter dependence of the effect of symmetry energy are discussed. It is found that in both central and semi-central collisions the sensitivity of the double n/p ratio to the density-dependent symmetry energy is more pronounced in neutron-richer systems. Our results also indicate clearly that the effect of symmetry energy is stronger in central collisions than that in semi-central collisions.

Three-body force effect on P-3 F-2 neutron superfluidity in neutron matter, neutron star matter, and neutron stars

We investigate the effect of microscopic three-body forces on the P-3 F-2 neutron superfluidity in neutron matter, beta-stable neutron star matter, and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the three-body force effect on the P-3 F-2 neutron pairing gap. It is found that the three-body force effect considerably enhances the P-3 F-2 neutron superfluidity in neutron star matter and neutron stars.