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.     

Vector analysing power of the pick-up reaction C(d, t)C

The vector analysing power has been measured for the reaction ¹³C(d, t)¹²C initiated by 12.1 MeV polarized douterons and proceeding to the ground and 4.43 MeV states of ¹²C. Large analysing powers were observed especially for the ground state reaction. The results have been compared with the predictions of the distorted waves Born approximation and with data for the ¹²C(d, p)¹³C reaction     

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.     

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.     

恒星氦燃烧关键反应12C(α,γ)16O天体物理S因子及其反应率

恒星氦燃烧阶段3α反应和12C（α,γ）16O反应相互竞争,两者的反应率共同决定了氦燃烧结束后12C与16O的丰度比,该比值是大质量恒星后继演化以及伴随的元素核合成过程的初始条件。目前,氦燃烧12C（α,γ）16O反应起始T₉=0.2处,天体物理模型要求的反应率的精确度要低于10%,然而尚未有实验或理论给出满足要求的结果。最为直接和可靠地获取12C（α,γ）16O反应率的方法,就是尽可能往低能区测量其天体物理S因子,然后通过理论外推到感兴趣的能区。为此基于经典的R-矩阵理论,建立了适用于低能核反应的多道、多能级的约化R-矩阵理论来拟合几乎所有可用的16O系统的实验数据。配合使用协方差统计和误差传播理论,拟合外推得到了客观的、内部自恰的和唯一性好的12C（α,γ）16O反应天体物理S因子。总的外推S因子STOT（0.3 MeV）=162.7±7.3 keV·b,理论上首次给出达到恒星演化与元素核合成模型的最低要求的S因子。基于计算给出的全能区的S因子,数值积分给出了温度位于0.04 6 T₉ 6 10的12C（α,γ）16O天体物理反应率。在T₉=0.2处,推荐的反应率为（7.83 ±0.35）×10-15 cm3mol-1s-1。During stellar helium burning, the rates of 3α and the 12C(α,γ)16O reaction, in competition with one another, determine the relative abundances of 12C and 16O in a massive star. The abundance ratio is the beginning condition of the following nucleosynthesis and star evolution of massive stars, which are extremely sensitive to the rate of 12C(α,γ)16O reaction at T₉=0.2. The most direct and trustworthy way to obtain the reaction rate of the 12C(α,γ)16O reaction is to measure the S factor for that reaction to as low energy as possible, and to extrapolate to energies of astrophysical interest. Based on a new multilevel and multichannel reduced R-matrix theory for applications in nuclear astrophysics, we have obtained an accurate and self-consistent astrophysical S factor of 12C(α,γ)16O, by a global fitting for almost all available experimental data of 16O system, with the coordination of covariance statistics and error-propagation theory. The extrapolated S factor of 12C(α,γ)16O was obtained with a recommended value STOT (0.3 MeV)=162.7±7.3 keV·b. And the reaction rates of 12C(α,γ)16O for stellar temperatures between 0.04 6 T₉ 6 10 are provided. At T₉=0.2, the reaction rate is (7.83 ±0.35)×10-15 cm3mol-1s-1, where stellar helium burning occurs.     

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.     

Spectroscopy of C

The ¹⁴C(t, p)¹⁶C reaction locates five new states in ¹⁶C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0⁺ and 2⁺ 2p-2h states, respectively. The 4.14 MeV state has J^π = 4⁺ and the 6.11 MeV state has J^π = 2⁺, 3⁻, or 4⁺.     

Potassium tetracyanoplatinate (II) trihydrate (K2Pt(CN)4·3H2O) studied by high resolution solid state C MAS NMR

Prudent analysis of the solid state ¹³C MAS NMR spectra of polycrystalline K₂Pt(CN)₄ · 3H₂O (KTCP)⁻ reveals that in crystals of this compound there are two types of carbon nuclei with slightly different ¹³C chemical shift tensors, contrary to what is found for the solution NMR spectrum and previous static powder NMR studies on this compound and the high resolution solid state NMR studies on other similar compounds. The ¹³C MAS spectra measured at different rotor spinning speeds are satisfactorily simulated though the use of a newly developed computer program based on a novel density matrix formulation. The present method is eminently successful even though the spectra are rather complicated because of (1) the relatively large anisotropies of the chemical shift tensors; (2) the high-order dipolar interactions between ¹³C and ¹⁴N nuclei because of the strong quadrupolar coupling constants of ¹⁴N nuclei; and (3) the indirect J-coupling between the ¹³C and ¹⁹⁵Pt. The principal elements as well as their orientations of the two ¹³C chemical shift tensors are evaluated from the spectral simulations.     

COHERENT π0 PHOTOPRODUCTION IN THE QUASI-Δ33 DOORWAY STATE MODEL

The quasi-Δ, doorway state model, previously developed to describe pion-nucleus scattering, ^[1] is applied to the study of cohe-rent π photoproduction on nuclei.The unifying features of this approach for pion elastic scattering and photoproduction are briefly discussed. The relationship to W. Weise's isobar-hole model calculation and plane wave impulse approximation calculations are examined. The results are presented for ¹⁶O(γ, π⁰)¹⁶O and ¹²C(γ, π⁰)¹²C, and compared with the available experimental data. It has a large suppression of cross section from the impulse approximation prediction.     

THE EXCITATION OF 9.5 MeV LEVEL OF 13C IN QUASI-Δ33 DOORWAY STATE MODEL

We have studied the excitation mechanism of 9.5 MeV Level of ¹³C in ¹³C(π^±,π^1±)¹³C (9.5 MeV) inelastic scattering in the framework of Quasi-X33 Doorway State. Model .Assuming. the transition to 9.5 MeV state is of a pure neutron has received satisfactory agreement with experiment. The results strongly suggest that the spin and parity assignment of state,9.5 MeV of ¹³C should be Jπ=9/2⁺.     

The contribution of 2N photon absorption in C(γ,2N) reactions for Eγ = 150–400 MeV

The ¹²C(γ,pn) and ¹²C(γ,pp) reactions have been studied using tagged photons of energy E_γ = 150–400 MeV. Recoil momentum distributions are compared to the results of Monte Carlo calculations based on a two-nucleon photon absorption model and two different phase space models. The ¹²C(γ,pn) data at low missing energy are consistent with absorption on 1p² and 1s1p nucleon pairs.     

Measurement of the average polarization of B produced by polarized muons in the μ + C → νμ + B reaction

The average polarization of ¹²B produced by the capture of polarized muons in ¹²C has been measured using recoil implantation techniques. From the result we deduce the average polarization of the ¹²B ground state ¹²B(0) corresponding to the ¹²C → ¹²B(0) Gamow-Teller reaction: J_μ(0) = 0.43 ± 0.10. The sizeable deviation of this polarization from the value of 2/3, characteristic of a “bare” 0⁺ → 1⁺ process, is a fair evidence for induced axial-vector interaction(s) in muon capture. The ratio of the induced pseudoscalar and the axial-vector coupling constants is deduced to be: g^μ_P/g^μ_A = 12 ± 5.     

Spin alignment in resonant C+O inelastic scattering

The spin alignment of the 3⁻ state (6.13 MeV) of ¹⁶O from inelastic scattering of ¹²C+¹⁶O has been measured in the energy region of known resonances around E_cm=20 MeV. The result, that the population of the m=±3 magnetic substates is enhanced on four resonances at 19.7, 20.5, 22.0 and 22.6 MeV, indicates the dominance of the aligned configuration on these resonances.     

Medium effects in coherent pion photo- and electroproduction on He and C

Coherent π⁰ photo- and electroproduction on ⁴He and ¹²C nuclei is investigated in the framework of a distorted wave impulse approximation in momentum space. The elementary process is described by the recently developed unitary isobar model. Medium effects are considered by introducing a phenomenological Δ self-energy. Recent experimental data for ⁴He and ¹²C can be well described over a wide range of energies and emission angles by the assumption that the Δ–nuclear interaction saturates.     

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°.     

The 15N and 13C solid state NMR study of intramolecular hydrogen bond in some Schiff's bases

A series of 11 Schiff's bases derived from substituted salicylaldehyde and aliphatic amines has been studied in the solid state by ¹⁵N and ¹³C cross-polarization magic angle spinning (CPMAS) nuclear magnetic resonance (NMR). ¹⁵N CPMAS is especially useful for investigation of the tautomerism in the compounds considered, owing to the large difference in the nitrogen chemical shifts of OH and NH tautomers. In the solid state, three of the compounds examined were shown by ¹⁵N NMR to exist as OH tautomeric forms, and the remaining eight as the corresponding NH forms. This was confirmed by ¹³C CPMAS. The results reported were compared with those obtained in CDCl₃ solutions.     

三环已基羧酸锡的13C和119Sn NMR研究

测定了33个三环己基脂肪族和芳香族羧酸锡在非配位溶剂(CDCl₃)中的¹³C和¹¹⁹Sn NMR谱。结果表明:化学位移δ(¹¹⁹Sn)值主要由锡原子的配位数决定,结构上微小的变化。都能在δ(¹¹⁹Sn)值上明显地表现出来。讨论了不同类型化合物间NMR参数间的关系。     

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.     

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.