Monte Carlo simulation of the decay of neutron resonances to determine resonance spins

The results for two types of experiments which measure the spins of neutron resonances is predicted by means of a Monte Carlo calculation which simulates the γ-cascades following neutron capture. The results are compared with experiment wherever possible. For the method which compares the ratios of γ-lines depopulating low-lying levels, the calculation is performed for ¹⁴³Nd, ¹⁴⁵Nd, ¹⁸⁷Os, and ¹⁸⁷Os. For the method which compares coincidence to singles counting rates, the calculation is performed for the four nuclei mentioned above plus ¹⁸⁵Re, ¹⁸⁷Re, and ¹⁷⁷Hf. The validity of the approximations and assumptions used in the calculation are discussed. Also discussed are proposed improvements in the experiments made on the basis of both experimental data and the calculation. All necessary derivations are given in the appendix.     

Generator-coordinate study of inelastic α + 12C scattering

A multi-channel calculation performed with the generator coordinate method is presented for α + ¹²C scattering. The inelastic channel α + ¹²C(2⁺) is included. Bound-state and resonance energies are determined for J^π = 0⁺ up to 6⁺. For the negative parity levels, the results are very similar to those obtained with a single-channel calculation. The positive parity resonances are more numerous and in better qualitative agreement with experiment in the multi-channel calculation. However, an incorrect value for the threshold energy α + ¹²C(2⁺) channel prevents one from obtaining a quantitative agreement with experiment.     

On the reduction of the Dirac equation to non-relativistic form: the dipole-dipole interaction in the hydrogen atom

Finite nucleus models are used in the calculation of the dipole-dipole part of the second-order hyperfine energy in the ground state of the hydrogen atom. The results are used as a guide to bring the non-relativistic calculation for a point nucleus into agreement with the relativistic calculation. This necessitates the introduction of delta function operators in the dipole-dipole operator and the zeroth-order hamiltonian. It is concluded that the reduction of the Dirac equation to non-relativistic form is valid for the hyperfine interaction up to order mc ²α⁶.     

Exact shell-model and projected Hartree-Fock calculations for Mg

The results of a projected Hartree-Fock calculation are compared with those of an exact shell-model calculation for states of J ? 6 in the nucleus ²⁴Mg. The realistic Kuo interaction is used, and gives reasonable agreement with experiment.     

Single-nucleon transfer reactions to 100Ru

Proton stripping and neutron pickup reactions have been studied to the levels of ¹⁰⁰Ru, a nucleus with collective properties that have been thoroughly studied. The neutron pickup results are consistent with a calculation for the neutron-hole structure of the J^π = 2⁺ phonon state. The proton stripping results show no resemblance to either the phonon structure calculation or to the prediction of a shell model with good seniority. Strong proton excitation of the known 8⁺ state at 3.06 MeV shows that this is not the four-boson state predicted by the ⊙IBA at that excitation.     

Noise in p+nn+ structures based on semiconductor compensated by doubly charged acceptors

The results are presented of a theoretical calculation of the spectra of generation-recombination and diffusion noise in p⁺nn⁺ structures whose base region is compensated by an impurity that creates doubly charged deep acceptor centers. The results of experimental studies of noise processes in such structures are provided. The theoretical results are compared with the experimental data.     

Static polarizabilities of helium and alkali atoms,and their isoelectronic ions

A rather simple method of calculation of the scalar and tensor components of static polarizability was developed for a wide range of atoms and ions. The general formulas for polarizabilities of SL terms, J levels, and F components of hyperfine structure are given. The results of calculation for ground and some excited states of He and alkali atoms (Li, Na, K, Rb, Cs) are presented. The comparison of the results with available theoretical and experimental data shows that, in most cases, the differences do not exceed 10%. The polarizabilities for the Li+, Be+, B²+, C³+, Ne⁷+, Mg+, Al²+, Si³+, Ar⁷+, Ca⁺, Sc²+, Ti³+, Sr⁺, and Ba⁺ ions are also given.     

A Numerical Calculation for Electron Impact Excitation of Copper

The scattering of electrons by atomic copper has been studied using Born approximation and the concept of the generalized oscillator strength (GOS). Differential and total cross-sections for the excitation of the 3d¹⁰ 4p² P state are calculated at incident energies of 100 eV and are compared with other available experimental and theoretical data. The agreement between our calculation for the differential cross-section and the available experimental results is fairly good at the forward angles, while the agreement at large angles is poor. The calculated total cross-sections are compared with the experimental data and those predicted by several theories. It is found that our calculation for the total cross-sections are in a good agreement with the close coupling calculation of Msezane and Henry (1986a, Physical Review A 33, 1631) for incident energies greater than 20 eV. The integrated cross-section measurements of Ismail and Teubner (1995, Journal of Physics B: Atomic, Molecular and Optical Physics 28, 4164) are in good agreement with the present calculation.     

Microscopic calculations for the 8Li system

A microscopic multi-channel cluster model calculation for the ⁸Li scattering system has been performed. Diagonal phase shifts, channel coupling strengths, and eigenphases are presented. For comparison, the ⁸Li bound and quasibound states have been investigated by a refined resonating group calculation. The results of both types of calculations are in excellent agreement. In the energy region up to the ⁵He-t threshold the calculated S-matrix elements, the energy eigenvalues, and the overlaps of the normalized functions with the eigenvectors explain the origin of the experimentally detected levels and moreover give predictions for the existence of additional levels.     

The two-body photodisintegration of 3He

The differential cross section for the reaction ³He(γ,d)¹¹H has been measured for proton energies 11–65 MeV. The results are compared with previous measurements and with a recent theoretical calculation.     

Theoretical calculation of beam quality factor of large-mode-area fiber amplifiers

In order to evaluate a fiber amplifier’s output beam quality, we have explored the beam quality factor calculation. A theoretical beam quality factor calculation method is presented in this paper. The method bases on modal power decomposition, laser rate equations and Fourier diffraction theory. Through the rate equations, each modal power weight factor at the fiber output facet is obtained. By the modal power decomposition, the optical field at the fiber output facet is established. Finally, running Fourier transformation, the beam diverging state in free space and corresponding M ² parameter are obtained. The calculation process is verified with applying it to working out the beam M ² parameters of large-mode-area (LMA) fiber amplifier system under different conditions. The numerical results help us well know and predict the out beam property. Some obtained results are also accord with other reporting outcomes.     

Description of the two-humped mass distribution of fission fragments of mercury isotopes on the basis of the multidimensional stochastic model

The dynamical model proposed earlier for describing fusion-fission reactions is applied to describing the two-humped mass distribution of fission fragments of mercury isotopes. In this model, the calculation of the time evolution of collective coordinates of the system is broken down into two stages. The first stage is that within which the projectile approaches the target nucleus, while the second is that of the evolution of the system formed after the touching of the projectile and target nuclei. The dynamical evolution of the system within both stages of the calculation is described on the basis of Langevin equations. The shell structure of colliding nuclei is taken into account at either stage of the calculation. Mass distributions are calculated for fragments originating from the fission of the mercury isotopes ^{190, 184}Hg formed in the fusion-fission reactions ⁴⁸Ca + ¹⁴²Nd → ¹⁹⁰Hg and ⁴⁰Ar + ¹⁴⁴Sm → ¹⁸⁴Hg. The process in which the isotope ¹⁸⁰Hg undergoes fission from the ground state is also calculated. The results obtained in this way are compared with the results of previous theoretical calculations and with available experimental data.     

Polyhedral variation and the projected Hartree-Fock approximation

A generalization of the Hartree-Fock approach is considered. The axially symmetric intrinsic state is oriented in a finite number of spatial directions, and a variational calculation is performed in the resulting subspace. A parametric representation of matrix elements between the rotated states is introduced. Some simple, as well as more complex polyhedral configurations are chosen. Calculations are carried out for ²⁰Ne, ²⁴Mg and ²⁸Si and the results are compared and analyzed. The case of ²⁴Mg is of particular interest, and the results are consistent with the observation that the intrinsic state should actually be non-axially symmetric.     

Influence of nucleon mean-free paths on intranuclear cascade results

Results of the intranuclear cascade calculation are compared for 62 MeV protons on ⁸⁹Y and ⁵⁴Fe targets. Standard calculations and results with mean free paths increased fourfold are compared. The latter set gives poorer results versus experimental data due to an overestimate of nuclear transparency.     

Multiple scattering effects for quasifree scattering in 3He(d,dd)1H breakup reaction

The differential cross sections for the ³He(d, dd)¹H breakup reaction have been measured in the kinematical region corresponding to quasifree scattering (QFS). The angular dependence of the cross section at the minimum laboratory energy of the unobserved proton has been obtained. The shapes of energy spectra are approximately reproduced by a calculation in the plane-wave impulse approximation (PWIA). As for the angular dependence of the cross section and for the absolute values, the calculation fails to reproduce the experimental results. A calculation with multiple scattering effects reproduces the experimental data well, not only for the shape of the energy spectra but also for the angular dependence. For the absolute cross sections, the ratio of the experimental values to the calculated ones with multiple scattering effects is 0.7 and this value is improved compared with the value of 0.3 obtained by the PWIA calculation.     

TiO基态 (X 3 Δr) 的势能函数与光谱常数

应用群论及原子分子反应静力学方法推导了TiO分子基态(X³Δ_r)的离解极限.采用不同的计算方法,包括密度泛函B3LYP,B3P86,BP86,B3PW91和MP2,MP4方法,结合不同基组计算了TiO分子基态的平衡核间距、能量和振动频率.研究表明,使用B3LYP方法,对O原子使用6-311+G基组,Ti原子使用6-311+ +G^**基组时计算得到的平衡几何结构、分子离解能和谐振频率与实验值符合得最好.使用优选出的方法和基组对T 关键词： TiO 势能函数 光谱常数 密度泛函理论     

Quantum-chemical ab initio study of the crystal-field and charge transfer energies of nanocrystalline Y2O3: Eu

The 4f energy levels and crystal-field parameters for several clusters representing the local coordination surroundings of Eu³⁺ in the bulk and nanocrystalline cubic Y₂O₃: Eu³⁺ crystals are obtained by using a method based on the combination of the DV-X_α calculation and the effective Hamiltonian method initialized by M.F. Reid et al. (J. Phys.: Condens. Matter, 2011, 23: 045501). The results are in reasonable agreement with the measured energy levels and the crystal-field parameters obtained from the least-square fitting. The charge transfer energies are also obtained for all the clusters from the DV-X_α calculation. The results indicate that, compared with the bulk Y₂O₃: Eu³⁺ crystal, the charge transfer band in the excitation spectra is red-shifted in the nanocrystal.     

α1 clusters in 12C

The results of a microscopic calculation for ¹²C states using bound state boundary conditions show that even for the lowest state, wave function components which describe two α-clusters plus one α¹ cluster in relative motion are important. Furthermore, there is evidence for excited states which contain one α¹ cluster.     

Dipole strength distribution and specific properties of excitations in the second minimum in actinide nuclei

Vibrational states in the first minimum in ²³⁸U and ²⁴⁰Pu and in the second minimum in ²⁴⁰Pu have been calculated within the quasiparticle-phonon nuclear model. The results of calculation of vibrational states in both minima are compared. Specific properties of the vibrational states in the second minimum in actinide nuclei are discussed.