Real Optical Potentials of Two-Carbon and Two-Oxygen Systems Using α-Particle

Using the independent a-particle model and the nuclear molecular orbital model, a real optical potential of an identical 4N-nucleus system is derived and used well to discuss the gross resonant phenomena of the elastic scatterings for ¹²C + ¹²C and ¹⁶O + ¹⁶O systems.     

Dominant angular momentum of gross structure in inelastic C+C(2) scattering

The gross structures observed at the CM energies of 24, 30 and 36 MeV in the angle-integrated ¹²C+¹²C(2⁺) cross section are attributed to contributions of the dominant angular momenta of 16, 18 and 20, respectively, based on analyses of the angular distributions. These assignments are shown to be favorable also for predictions of other available data such as particle-γ correlations, alignments of the spin substates and the elastic excitation functions.     

A Description of the 12C+12C Scattering Excitation Function by an α-Folding Potential

A folding potential constructed from the point of view of the α-Particle structure of the nucleus ¹²C can well reproduce the recent experimental data of the ¹²C+¹²C elastic excitation function at θ = 78°.     

On the Difference and Similarity Between Elastic Scatterings of Ne + C and O + O1

Based on the LCNO model with double alpha transfer and on the optical model, the experimental excitation functions and the angular distributions of ²⁰Ne + ¹²C and ¹⁶O + ¹⁶O elastic scatterings are respectively reproduced by using approximately equal parameters of optical potentials. The difference and the similarity exhibited in the elastic scattering excitation functions of these two systems are naturally explained.     

K+ Inelastic Scattering From 2+, 3- State of 12C at 800 MeV/c

The differential cross sections of the inelastic scattering 6f K⁺ at 800 MeV/c on 2⁺, 3^- excited states of ¹²C are calculated by means of the eikonal approximation and the collective coordinate. It seems that the 2⁺ state of ¹²C is quadrupole rotational state, the 3^- state of ¹²C is octupole vibrational state. The results are in agreement with experimental data.     

Analysis of the scattering of 46 MeV protons from Be and C

An analysis is made of the measurements of the elastic and inelastic scattering of 46 MeV protons by ³Be and ¹²C. The optical and collective models are used. There is considerable ambiguity in the optical parameters, and it was not found possible to obtain good fits to cross sections and polarizations simultaneously. Large quadrupole deformations were found for both ¹²C (β₂ ≈ 0.6) and ⁹Be(β₂ ≈ 1). The inelastic scattering from ¹²C agrees best with deformation of both real and imaginary parts of the optical potential, while ⁹Be shows a preference for real coupling. The 14.1 MeV level in ¹²C is interpreted as the 4⁺ rotational state, while the angular distribution for the 7.6 MeV 0⁺ level is well described by double quadrupole excitation via the lowest 2⁺. Interpretations are suggested for other inelastic transitions, including the excitation of spin and isospin oscillations.     

An Investigation of 4He+12C and 4He+16O Reactions Using the Cluster Model

The α -target semimicroscopic single folding potentials have been derived by folding a composite (repulsive and attractive) effective α-α interaction with the α -cluster distribution density in the target nuclei. The obtained potentials are considered as the real part of the nuclear optical model potentials, while the imaginary parts are phenomenologicaly expressed using the Woods-Saxon form. Nine sets of measured experimental data of the ⁴He+¹²C and ⁴He+¹⁶O elastic rainbow scattering over the energy range 80-240 MeV are analyzed using the obtained potentials. The data are successfully reproduced using the extracted potentials. The resulted reaction cross sections are also investigated and compared with the available corresponding data.     

12C+13C在库仑位垒以下能区的熔合截面测量

深垒下能区的12C+13C熔合截面测量对检验天体中熔合反应外推模型具有很重要的意义。目前在库仑位垒以下能区存在的各种测量结果,都利用了统计模型来修正得到熔合截面,但对于这些方法间的系统误差仍没有很好地研究。实验采用离线活度测量的方法,在E_c.m.=4.4～5.8 MeV能区内对12C+13C熔合截面进行测量。经Hauser-Feshbach统计模型对分支比的修正后,熔合总截面由24Na活度推导出。通过本实验数据与其它实验方法获得的数据进行比较,确定了统计模型的系统误差为14%。The study of fusion reactions of 12C+13C at the deep sub-barrier energies is very important for the test of predictive power of the extrapolation models for nuclear reactions for astrophysics. Until now, all the measurements below Coulomb barrier energies have to use the statistical model calculations to estimate the branching ratios to deduce the total fusion cross sections. However, the systematic uncertainty induced by the calculated corrections has not been studied well. In this experiment, the fusion cross sections of 12C+13C have been measured using an offline activity measurement in the range of E_c.m.=4.4 to 5.8 MeV. The total fusion cross sections have been deduced from the 24Na activities after correcting the branching ratios estimated with the Hauser-Feshbach statistical model. Through the comparison between our result and other data obtained with other methods, the systematic uncertainty of statistical model has been determined to be 14%.     

Electroproduction of π from C leading to low-lying residual states in B

Energy distributions of π⁺ produced from ¹²C by electrons of total energy 195 MeV were measured at various angles. The results show large contributions from transitions leaving the residual nucleus in the ground (1⁺), first (2⁺) excited state and states at around 4.5 MeV. The angular distributions of ¹²C(γ, π⁺)¹²B leading to these residual states are deduced from the energy distributions by the unfolding method with the virtual photon theory. Theoretical results with the Helm model and the shell model are compared with the experimental results. Their relative shapes are in good agreement. A better agreement in the absolute value is found for the theoretical results which include the final-state interaction estimated with a pion optical potential. The surface production model shows better agreement with the experimental (γ, π⁺) cross sections than the volume production model.     

The Quantum Group Theoretic Approach to Heavy-Ion Resonances

We suggest the quantum group as dynamical symmetry group of heavy-ion resonance systems. The rotation-vibrational spectra of the systems are given by the quantum groun theoretic approach without going to the detail of the bonding potential of the systems. The corresponding wave functions are obtained. Using the analytic formula of this approach, we fit the experimental data of ¹²C+¹²C and ¹²C+¹⁶O resonance systems in high accuracies. The pseudepotential is found in the quantum group symmetric model and discussed in comparison with the conventional nonlinear potential model.     

Final-state interaction effects in exclusive and inclusive quasi-elastic electron scattering from C

Nucleon emission in the quasi-elastic region is studied for the ¹²C(e, e'p) and ¹²C(e, e'n) reactions. We present a model which couples the one-nucleon emission channels microscopically and treats the multi-nucleon emission channels phenomenologically. We analyze the spectral functions extracted from the ¹²C(e, e'p)¹¹B reaction measured at NIKHEF-K and Saclay and make predictions for the ¹²C(e, e'n)¹¹C spectral functions. The ratio of the ¹²C(e, e'p)¹¹B and ¹²C(e, e'n)¹¹C spectral functions is found to depend strongly on the two-nucleon interaction. We analyze the contribution of the one-proton and one-neutron emission channels to the inclusive longitudinal and transverse response functions. Our analysis suggests the importance of multi-nucleon emission in the quasi-elastic region. The ratio of the experimental transverse-to-longitudinal structure functions is satisfactorily reproduced.     

Unconventional Medium Effect in K+-and π+-Nucleus Scattering

The ratios of total cross section of K⁺-nucleus to K⁺-deuterium at 400 MeV/c≤pk≤800 MeV/c for ⁶Li, ¹²C, ²⁸Si, ⁴⁰Ca and the differential cross section of π⁺-¹²C scattering at p_π= 800 MeV/c are calculated by taking into account the unconventional medium effect.An enhancement of both the K⁺-and π⁺-nucleus scattering cross sections is obtained.     

Analysis of Neutron Double-Differential Cross Sections for n ＋ ^12 C Reaction Below 30 MeV

Based on the light nucleus reaction model （Nucl. Sci. Eng. 133 （1999） 218）, four aspects （neutron incident energy region, reaction channel analysis, the renewed level schemes and the optical model parameters） of n＋ ^12 C reaction are improved to calculate total outgoing neutron double-dilferential cross sections with modified LUNF code below 30 MeV. The calculated results agree fairly well with the experimental data at En = 14.1 MeV and 18 MeV. The analysis shows that the pre-equilibrium mechanism, which is exactly considered the conservation of energy, momentum and parity, dominates the whole reaction process. The contribution of the neutron emission from 5He to total energy- angular spectra is also considered properly. This modified LUNF code will be a useful tool to set up the file of neutron double-differential crass sections below 30 Me V in the neutron evaluation nuclear data library.     

The two-neutron transfer reactions (O, O) with O, C and Mg targets

Excitation functions, angular distributions and differential ranges were measured for the ²⁶Mg(¹⁸O, ¹⁶O)²⁸Mg reaction at ¹⁸O beam energies of 20–45 MeV. Excitation functions only were measured for the reactions ¹⁴C(¹⁸O, ¹⁹O)¹³C, ¹⁴C(¹⁸O, ¹⁶O)¹⁶C, ¹⁴C(¹⁸O, ²⁰O)¹²C, ¹⁴C(¹⁸O, ¹⁵N)¹⁷N and ¹⁸O(¹⁸O, ¹⁹O)¹⁷O, ¹⁸O(¹⁸O, ¹⁶O)²⁰O, ¹⁸O(¹⁸O, ¹⁵N)²¹F at ¹⁸O beam energies of 13–41 MeV. We have identified these as direct reactions in which a single neutron, a two-neutron cluster, a deuteron and a triton are transferred between projectile and target.

The cross sections for two-neutron transfer reactions were found to be relatively high and those for the ¹⁸O+¹⁸O and the ¹⁴C+¹⁸O reactions were higher than the ones of single-neutron transfers over most of the energy range.

Attempts were made to apply the theory of Buttle and Goldfarb for single-neutron transfer to the case of two-neutron transfer in the ²⁶Mg(¹⁸O, ¹⁶O)²⁸Mg reaction below the Coulomb barrier. It is shown that for those reactions for which the assumptions, implicit in the model, are valid, good agreement is obtained with experiment. We also tried to apply the diffraction model of Dar and Kozlovsky to the calculation of the angular distribution of these reactions. A good fit to the experimental results could be obtained if quite different sets of parameters were used in the calculations for the two bombarding energies.     

Energy spectra of neutrons emitted following muon capture in O and C

The energy spectra of neutrons emitted following muon capture in ¹⁶O and ¹²C are investigated using the continuum shell model. Nuclear wave functions, which have been shown by Ohtsubo and the author to describe the radiative pion capture reaction in the above nuclei well, are adopted. The calculated neutron energy spectra explain well the observed main peaks, at 5 MeV for ¹⁶O and 4 MeV for ¹²C, which are considered to be the giant resonances excited in the muon capture reaction. These peaks are interpreted as the 2⁻ state at 20.3 MeV for ¹⁶O and the 1⁻ state at 22.5 MeV for ¹²C. Comparisons with photon spectra in radiative pion capture reactions are also made. The calculated total capture rates exceed the experimental values by a factor of 2.5 for ¹⁶O and by 30–40% for ¹²C.     

Effect of the adiabatic process on the absorption in heavy-ion scattering

We have succeeded in obtaining the optical model potential for ¹²C---¹²C scattering at low incident energies (10 MeV E_cm 20 MeV), by applying the adiabatic approximation to the coupled channels equation. As for this potential inelastic channels of single and mutual excitations of ¹²C^*(2⁺, 4.43 MeV) make a contribution to the real part and not to the imaginary part.     

(C_5H_(11)N_2)~+和(C_7H_(12)N_2)~(2+)的NMR研究

结合1H NMR,13C NMR谱,分别对钨、钼配合物{WO2(C10H6O2)2(C5H11N2)2[H2N(CH2)3NH2]}3(1),{(C5H11N2)2[H2N(CH2)3NH2][MoO2(C10H6O2)2]}(2),{(C7H12N2)2[MoO2(C10H8O2)2]}(3)晶体结构中小分子环进行了归属.其中,配合物1和2中(C5H11N2)+的NMR研究证实了六元环由1,3-丙二胺和乙腈化合而成,配合物3中(C7H12N2)2+的NMR谱图证实了七元环由乙二胺和乙酰丙酮化合而成,并且推导出这些亲核加成-消除反应的反应机理.配合物1~3中的小分子环的合成在其它体系中尚未见报导,而在合成它们的反应中作为新产物随主体晶体析出,并由晶体结构解析和NMR得到了证实.     

The Deep Potential Description of Backward-Angle Anomalous Behavior for a-Type Nucleus Elastic Scatterings

Within the framework of the optical model, the backward-angle anomalous behaviors of the angular distributions for the ¹⁶O+²⁴Mg and the ¹⁶O+²⁸Si elastic scatterings have been well described by using deep optical potentials. The excitation functions of elastic scattering for the ¹⁶O+²⁴Si system at θ _cm = 90° and 180° have also been reproduced well by using the same set of deep potential parameters. The results show that the effect of the deep potential resonance may be responsible for the backward-angle anomalous behavior.     

Inelastic Pion Scattering from 12C at 800 MeV/c

The differential cross section of the inelastic scattering of pion at 800 MeV/c fir the 3^- excited states of ¹²C is calculated by making use of eikonal approximation and the collective coordinate. The calculation indicates that the 3_- state of ¹²C is octupole vibrational state.The results are in agreement with experimental data.