12C快中子辐射俘获反应中的共振现象

主要研究中子辐射俘获反应中的共振现象,利用DSD模型计算激发能量在5—25MeV能区的¹²C(n,γ0)反应截面与E_n=9MeV时的角分布.所考虑的反应机制包括复合核俘获、直接和半直接俘获、复弹性和非弹性散射道的辐射俘获.计算表明,矮共振的峰值在激发能量为13MeV处;巨共振的峰值位置在激发能量21MeV处.计算结果与实验符合较好.     

17C反应截面和去中子截面

利用日本理化学研究所的放射性束流线RIPS, 测量了能量为79A MeV的¹⁷C在¹²C反应靶上的反应截面, 并同时得到了¹⁷C的移去1个、2个及3个中子的截面; 分别利用有限力程Glauber模型和少体Glauber模型结合壳模型的谱因子分析了反应截面和移去1个中子截面, 研究了¹⁷C的密度分布、结构和价中子布居. 反应截面和中子移去截面是两个相互独立的量, 通过对两者的分析, 都可以得出¹⁷C由芯核¹⁶C和价中子组成, 并且价中子主要处于d_5/2轨道的结论. 总结了现有的碳同位素的反应截面和相互作用截面的工作.     

The Reaction Cross Section and Neutron Removal Cross Sections of 17C

The reaction cross section, together with the one-, two- and three neutron removal cross sections, of ¹⁷C with the energy of 79A MeV on carbon target were measured using the radioactive beam line RIPS of RIKEN. The reaction cross section and the one-neutron removal cross section were analyzed within the frame of Glauber model. Both the analyses favor the dominant configuration of a ¹⁶C core (2⁺) plus a d_5/2 valence neutron for ¹⁷C. The work for the neutron-rich carbon isotope on the reaction cross section σ_R and the interaction cross section σ_I on ^{12C target are summarized.}     

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.     

轻丰中子核反应中子集团产生截面的理论研究

采用Boltzmann-Langevin方程研究了能量为35MeV/u的¹⁴Be, ⁸He,⁶He,¹¹Li,¹⁷B,¹¹Be,¹⁹C与¹²C靶的反应,计算了产生中子集团的截面, 发现^14,Be与¹²C靶反应产生⁴n的截面与实验值符合得很好. 通过这几个入射核与¹²C靶形成中子集团截面的对比, 发现核的晕中子越多产生中子集团的截面越大, 晕中子数相同时, 质量数越大产生中子集团的截面越大.中子集团可能主要来自晕核子.     

Interaction of 80 MeV12C with88Sr; Neutron transfer,inelastic scattering and spin alignment of the 2+ State of12C

Level structure of¹⁰²Cd has been studied via both¹⁰²In decay and nuclear reactions. Using⁹²Mo+¹⁴N at 86 MeV, the nucleus¹⁰²In was identified and its decay (T _1/2=24 ±4s) studied with the aid of on-line mass separation techniques. Levels of¹⁰²Cd were also populated with⁹²Mo+¹²C at 50 MeV and¹⁰²Pd+³He at 35 MeV reactions and investigated by means of standard in-beam techniques. A level scheme including states up to 4.5 MeV excitation energy is proposed and then discussed in the frame of available calculations.     

Analysis of the Fourier transform spectrum of 13C18O2 in the 4.3- and 16-μm regions

Fourier transform spectra have been obtained for ¹³C¹⁸O₂ in the regions of ν₂ (16 μm) and ν₃ (4.3 μm) at a resolution of 0.04 cm^?1. From a least-squares fit of the P- and R-branch lines for the transitions, values have been calculated for the rotational constants B, the centrifugal distortion constants D, and the band origins. Based on the derived constants, the calculated wavenumbers for the P and R lines of both the 01¹0-00⁰0 and 00⁰1-00⁰0 transitions agree with the observed positions within ±0.003 cm^?1. We have also observed the difference bands ν₁-ν₂ and the hot bands (ν₃ + ν₂) ? ν₂. From an analysis of these transitions we have determined values for the l-doubling constants for ν₂ and the location of the inactive fundamental ν₁.     

Neutron branching in the reaction 12C + 12C

The cross section for the reaction ¹²C(¹²C, n)²³Mg has been measured in the energy range E_c.m. = 3.54?4.94 MeV by counting the delayed γ-rays from ²³Mg decays (half-life = 11.57 sec), and a theoretical model has been employed to extrapolate the results to threshold (E_c.m = 2.60 MeV). By combining these results with previous measurements of the reactions ¹²C(¹²C, p)²³Na and ¹²C(¹²C, α)²⁰Ne, the neutron branching ratio in the energy interval from threshold to 8 MeV is deduced, and a thermal average is computed that should be valid for use in astrophysical environments characterized by temperatures in the range (0.5–5) × 10⁹ °K. The neutron branching at temperatures appropriate to hydrostatic carbon burning in stars (T ≈ 109 °K) is found to be much smaller than previously estimated.     

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

Based on the light nucleus reaction model (Nucl. Sci. Eng. l33 (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-differential 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 energyangular spectra is also considered properly. This modified LUNF code will be a useful tool to set up the file of neutron double-differential cross sections below 30 MeV in the neutron evaluation nuclear data library.     

Neutron Structure of the Ground State of 7He

JETP Letters - A study of the neutron structure of the ground state of 7He has been performed by means of registration and analysis of the decay channels of the residual nuclei following absorption...     

Reaction Rate of Radiative Capture of a Neutron by a 2H Nucleus

Russian Physics Journal - Within the framework of the modified potential cluster model with forbidden states, n2H radiative capture is considered at energies from 10 meV (0.01 eV) to 10 MeV. It is...     

13C的一个可能的类晕的中子2p态

假设13C是单粒子的2p态的结构,用Glauber多重散射理论研究了入射能量为1GeV的质子在13C上的弹性散射,得到了与实验符合得很好的理论结果.这说明13C可能存在着一个类晕的中子皮.     

Halo Structure of 19C via the (p,d) Reaction

 We have investigated the heaviest one-neutron halo candidate, the ¹⁹C nucleus. Few-body model calculations of cross-section angular distributions for the ¹⁹C(p,d)¹⁸C reaction together with test calculations carried out for the ¹⁷C(p,d)¹⁶C reaction at a low incident energy are presented for different possible halo-neutron configurations. We show that there is a clear distinction in particular between l _n  = 0 and l _n  = 2 halo transfers. The sensitivity of the cross sections to the assumed ¹⁹C single-neutron separation energy is discussed. Received October 13, 1999; revised November 25, 1999; accepted for publication April 29, 2000     

14C激发态中子晕

利用¹³C(d,p)¹⁴C反应实验数据,抽取转移反应重叠函数渐近归一化常数,计算了¹⁴C的1^－和0^－激发态的最后一个中子的密度分布的均方根半径和在核外的几率.研究结果表明,¹⁴C的1^－和0^－激发态为中子晕态.     

Absolute line wavenumbers in the near infrared: 12C2H2 and 12C16O2

40 absolute line wavenumbers in the 3v ₃ band of ¹²C¹⁶O₂ between 6927 cm^?1 and 6989 cm^?1 and 626 absolute line wavenumbers in the near infrared absorption spectrum of ¹²C₂H₂ between 7060 cm^?1 and 9900 cm^?1 have been measured using high resolution Fourier transform spectroscopy. The calibration of the CO₂ line wavenumbers relied on heterodyne frequencies available in the v ₁ + v ₃ band of ¹²C₂H₂ near 6556 cm^?1. The absolute uncertainty of the calibrated CO₂ line wavenumbers is estimated to 0.000 08 cm^?1. The acetylene spectra were calibrated using heterodyne frequencies available in the 2—0 band of ¹²C¹⁶O and the line wavenumbers obtained in the 3v ₃ band of ¹²C¹⁶O₂. The absolute uncertainty of the calibrated acetylene line wavenumbers is estimated to range from 0.0003 cm^?1 to 0.006 cm^?1 for strong to very weak isolated lines. Comparison with absolute line wavenumbers obtained independently at JPL in the 3v ₃ band of ¹²C₂H₂ near 9649 cm^?1, calibrated using absolute wavenumbers available in the 2—0 and 3—0 (near 6350 cm^?1) bands of ¹²C¹⁶O, shows very good agreement. Also, the vibration—rotation constants for the observed upper vibrational states of ¹²C₂H₂ were determined, but without accounting for the perturbations affecting these states.     

First Observation of the Forbidden k-X Transition of (13)C(16)O

A weak rotationally resolved absorption band of (13)C(16)O has been identified from photographic spectra at 1078 ? and assigned to the forbidden transition from the X(1)Sigma(+) (v = 0) ground state to the k(3)Pi (v = 3) valence state. It is similar in structure to the corresponding band of (12)C(16)O but due to the fact it was photographed at a relatively low pressure only the two strongest rotational branches could be positively identified. It is the first time that the forbidden k-X transition has been observed for (13)C(16)O. The measured isotopic shift in the band origin provides independent confirmation of the new vibrational assignment of the k state by G. Berden, R. T. Jongma, D. Van der Zande, and G. Meijer (J. Chem. Phys. 107, 8303-8310 (1997)). Copyright 2000 Academic Press.     

Lifetime measurement of the first excited 2+ state in 16C

The lifetime of the 2_+(1) state in 16C has been measured with the recoil distance method using the 9Be(9Be,2p) fusion-evaporation reaction at a beam energy of 40 MeV. The mean lifetime was measured to be 11.7(20) ps corresponding to a B(E2;2_+(1)-->0+) value of 4.15(73)e_2 fm_4 [1.73(30) W.u.], consistent with other even-even closed shell nuclei. Our result does not support an interpretation for "decoupled" valence neutrons.     

OH分子基态和第一激发态的势能函数

采用多参考组态作用(MRCI)方法和aug-cc-pVTZ,aug-cc-pVQZ,cc-pV5Z,6-311++g(d,p)和6-311++g(3df,3pd)几个不同基组对OH分子的基态(X²Π)和第一激发态(A²Σ⁺)的势能曲线进行计算.选用Murrell-Sorbie势能函数对曲线进行拟合,利用拟合的参数值计算出力常数和光谱数据.结果表明计算值与实验值吻合较好.     

Search for 8+ strength in 16O via the 12C(α, α2)12C1(7.66 MeV) reaction

Closely spaced angular distributions have been measured for the ${}^{12}\text{C}\text{(α, α}{}_2\text{)}{}^{12}\text{C}\text{1(7.66}\text{MeV}\text{)}$ reaction between E_α = 17.39 and 20.5 MeV in a search for 8⁺ strength in ¹⁶O. No evidence of 8⁺ strength is found, but evidence is found for a narrow 7^? resonance at 21.52 MeV excitation.