New shadowing corrections to photon-deuteron total cross sections

The Glauber correction to photon-deuteron total cross sections is reexamined in the light of the Extended Vector Dominance Model. If the photon couples to an infinite number of π-like vector mesons one obtains an extra shadowing correction of about 3 μb at high energy. Some of the consequences of this new contribution are briefly discussed.     

Coulomb polarization corrections to the cross sections of nucleosynthesis at low energies

The effects of electric polarizability of particles are shown to play an insignificant role in nucleosynthesis reactions at astrophysical low energies. The polarization corrections to S-factors of the reactions under consideration are defined by the value of the polarization potential at the boundary of the nuclear force range and do not exceed the quantity of the order of 0.1%.     

On total photon cross sections and contributions of the new quark states

The vector dominance model is used to calculate the contributions of the ψ-family to total photon cross sections, the parameters being estimated from the radiative and leptonic decays of the ψ-states. This is found to be rather small when compared to the recent data of Caldwell et al. on σ_tot(γp) at Fermilab energies. To explain this discrepancy, it is then conjectured that, within the context of VDM, one may have to invoke the recently hypothesized multiquark states to give the observed increase in σ_tot(γp); upper limits are set on their contributions.     

Relativistic recoil and spin corrections to atomic and Coulomb wave functions

A new wave equation for the relativistic two-body problem is derived and shown to be equivalent to the Breit equation and also to the “quasipotential” equation. Its unique advantage is that it provides analytic wave functions for arbitrary combinations of masses, spins, magnetic and higher moments of the two particles. Various applications are indicated, including an improvement of Dirac wave functions at small distances.     

On the calculation of scattering cross sections from absorption cross sections

A dispersion-type relation between photon scattering and absorption cross sections is derived. It is shown that the relation gives the correct scattering cross section in the low and high frequency limits, and is consistent with the Kramers-Heisenberg formula in the vicinity of a resonance. The practical application of the relation is illustrated by calculations of the scattering cross section and refractive index of He and Ne at STP and dry air at 1200°K from known absorption cross section data. The method is useful for obtaining scattering cross sections, polarizabilities, and refractive indices at elevated temperatures.     

J-matrix method for calculations of three-body Coulomb wave functions and cross sections of physical processes

The review is devoted to a widely known method of numerical solution to the three-body Coulomb problem, namely, the J-matrix method. Special attention is paid to ways of solving the Lippmann-Schwinger integral equation without attraction of pseudostates. Difficulties related to the formulation of the integral equation in spherical coordinates, leading to the divergence of its integral part if the wave function is calculated with two asymptotically free electrons, are demonstrated. In addition, the relation between exact and approximate solutions turns out to be unclear if the matrix of a residual potential is restricted to a finite number of basis functions, with the latter being increased. It is shown that, in principle, these problems can be avoided by reformulating a problem in parabolic coordinates.     

Calculations of one-loop supersymmetric corrections to large-E_T jet cross sections

We have calculated the one-loop supersymmetric corrections to the parton scattering subprocesses and , including form-factor corrections and box diagrams with internal squarks and gluinos of arbitrary mass. In general, these exhibit cusps at the corresponding direct-channel sparticle thresholds. We use these calculations to make numerical estimates of the possible threshold effects at the Fermilab Tevatron collider and at the LHC, which depend on the rapidity range selected, but can be as large as a few percent. These effects are diluted in the integrated large- cross section, where they are negative. Received: 18 August 1997 / Published online: 20 February 1998     

转动喇曼散射截面的群论计算

本文利用群链U(4)U(3)O(3)描述双原子分子N_2和O_2振转谱的对称性质,并利用群论方法计算了N_2和O_2分子转动喇曼散射的跃迁矩阵元,给出了它们的转动喇曼散射的截面。结果与实验较好地符合。     

Coulomb and photo cross sections for nucleon emission from relativistic O projectiles

Coulomb cross sections for nucleon emission out of ¹⁶O projectiles scattered with laboratory energies of 2.1, 60 and 200 GeV/nucleon on various target nuclei are calculated in first-order perturbation theory by using the corresponding photo cross sections. The photo cross sections are obtained with an 1-particle-1-hole basis in the giant resonance region and with the quasi-deuteron model up to photon energies of 140 MeV. Whereas the 2.1 GeV/nucleon results agree well with the experimental data points, the 60 and 200 GeV/nucleon cross sections are roughly one quarter lower than the measured ones, because also photons with energies higher than 140 MeV contribute at these incident energies.     

He-NO碰撞体系分波截面的理论计算

首先用Huxley势函数拟合在RCCSD(T)/aug-cc-pVTZ bf理论水平下计算的He-NO相互作用能数据,从而得到了He原子与NO分子相互作用各向异性势;然后用密耦近似方法计算了He-NO碰撞体系的总分波截面、弹性分波截面和非弹性分波截面,并总结了分波截面的变化规律.计算结果表明,拟合势较好地描述了He-NO系统相互作用的各向异性特征,利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题,对进一步研究原子与分子碰撞机理有一定参考价值.     

A semi-empirical method for the calculation of spin—orbit splitting in degenerate electronic states of linear polyatomic molecules

A semiempirical method for the calculation of spin—orbit coupling constants in linear polyatomic molecules is discussed. The method uses the readily available output from a CNDO/2 calculation and a set of effective atomic coupling constants obtained from observed spectroscopic data on atoms. Two procedures for obtaining the spin—orbit splitting are discussed: one based on a closed shell CNDO/2 calculation and one based on an open shell calculation.The average error for the molecules studied was 6.8% and 7.7% for the two procedures used in the calculations, the easier closed shell procedure giving the lower percentage error. It should be noted that the largest errors occurred in the case of diatomic molecules where the error would be expected to be the greatest. Thus, the average error involved in the values of the spin—orbit splitting for polyatomic molecules is much less than 3.7% for the closed shell procedure. The method used appears to be extendable to non-linear molecules in which the only atoms off the principle symmetry axis of the molecules are hydrogen. The method should be useful in the interpretation of photoelectron spectra.     

Measurement of the neutrino-nucleon and antineutrino-nucleon total cross sections

The v and $\text{v}$ nucleon total cross-sections have been determined as a function of energy using a sample of 2500 v and 950 $\text{v}$ event. The results are compared with predictions of scaling and charge symmetry hypotheses.     

A semi-empirical method for the calculation of spin—orbit splitting in degenerate electronic states of linear polyatomic molecules

A semiempirical method for the calculation of spin—orbit coupling constants in linear polyatomic molecules is discussed. The method uses the readily available output from a CNDO/2 calculation and a set of effective atomic coupling constants obtained from observed spectroscopic data on atoms. Two procedures for obtaining the spin—orbit splitting are discussed: one based on a closed shell CNDO/2 calculation and one based on an open shell calculation.The average error for the molecules studied was 6.8% and 7.7% for the two procedures used in the calculations, the easier closed shell procedure giving the lower percentage error. It should be noted that the largest errors occurred in the case of diatomic molecules where the error would be expected to be the greatest. Thus, the average error involved in the values of the spin—orbit splitting for polyatomic molecules is much less than 3.7% for the closed shell procedure. The method used appears to be extendable to non-linear molecules in which the only atoms off the principle symmetry axis of the molecules are hydrogen. The method should be useful in the interpretation of photoelectron spectra.