Deep spallation cross sections in high energy protons — Uranium interactions

Cross sections of deep spallation products — from phosphorus to hafnium — formed in uranium by high energy protons (E _p ? 10 GeV) have been calculated with a simple semi-empirical formula. The results are in excellent agreement with experimental data.     

The K–nucleus cross sections in relativistic non-linear models

The K⁺−nucleus cross sections have been calculated in relativistic non-linear models taking into account the in-medium modifications of nucleons and mesons properties. More precisely, we have taken into account both the dressing of the nucleon effective mass by the scalar nuclear field in the target and the coupling of the mesons exchanged between the K⁺ and the nucleons to the polarization of the medium. First, using the most recent relativistic non-linear models, the in-medium σ, ω and ρ meson masses have been obtained in the nuclear matter rest frame. The influence of the non-linear contributions on the K⁺−nucleus cross sections has then been studied. Finally, we have compared our results with the experimental data.     

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.     

The photonuclear cross sections of 48Ca

The sum of the photoneutron and photoproton cross sections of ⁴⁸Ca (⁴⁸Ca(γ, n + p)), has been deduced from an activation yield curve measurement using bremsstrahlung. In a separate experiment the ⁴⁸Ca(γ, p) and partial photoproton cross sections to the ground and first excited states of ⁴⁷K have been deduced from measured photoproton spectra recorded from the electro-disintegration of ⁴⁸Ca. The ⁴⁸Ca(γ, n) cross section is estimated from these data. A statistical decay model is used to estimate the ⁴⁸Ca(γ, 2n) cross section. These reported cross sections are used to determine the relative strengths and energy distributions of the isospin components of the GDR states, and to compare these with theoretical predictions.     

Electron-impact excitation cross sections for neon

An analytic atomic independent particle model adjusted to experimental single-particle energy levels is used to generate wavefunctions for the excited states of neon. Using these wavefunctions in conjunction with the Born approximation and the Russell-Saunders LS-coupling scheme, we calculate generalized oscillator strengths and cross sections for electron-impact excitation of neon from the 2p⁶(¹ S ₀) ground state.     

Infrared absorption cross sections for methanol

Infrared absorption cross sections for methanol, CH₃OH, have been determined near 3.4 and 10 μm from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125HR) and a multipass cell with a maximum optical path length of 19.3 m. Methanol/dry synthetic air mixtures were prepared and spectra were recorded at 0.015 cm^?1 resolution (calculated as 0.9/MOPD) at a number of temperatures and pressures (50–760 Torr and 204–296 K) appropriate for atmospheric conditions. Intensities were calibrated using composite methanol spectra taken from the Pacific Northwest National Laboratory (PNNL) IR database. The new measurements in the 10 μm region indicate problems with the existing methanol spectroscopic line parameters in the HITRAN database, which will impact the accuracy of satellite retrievals.     

Theoretical cross sections for keV antiprotons

Partial and total close-coupled semiclassical (impact parameter) cross sections and total classical Monte-Carlo cross sections for interactions in and , p+H collisions are computed in the intermediate keV range for antiprotons, , up to 100 keV lab. Total cross sections for antihydrogen, , formation are found to be large, 10−20×10⁻¹⁶ cm² in a wider energy range than was anticipated earlier, up to some 20 keV lab. New estimates of cross sections for ionisation of atomic hydrogen by antiproton impact are reported for the low-energy range 1–30 keV lab where they are 10−20×10⁻¹⁷ cm², being much larger than the corresponding cross sections for ionisation of hydrogen by proton impact. Data for excitation of H by impact is also presented.     

Elastic cross sections for electron--carbon scattering

We used the close-coupling optical (CCO) approach to investigate the open-shell carbon atom. The elastic cross sections have been presented at the energies below 90eV, and the present CCO results have been compared with other theoretical results. We found that polarization and the continuum states have significant contributions to the elastic cross sections. The present calculations show that the CCO method is capable of calculating electron scattering from open-shell atoms.     

Universality tests for total cross sections

Starting directly from data we test the universality of the decomposition of total cross-sections in an asymptotically dominant term, the Pomeron, and a non dominant one, the Reggeon. Without assuming Regge pole model behaviour or additive quark model relations we show that data are compatible with both models. Support is not found for models predicting asymptotical equality of total cross-sections.     

The correction of coincidence electron-scattering cross sections for radiative effects

The correction of inelastic electron-scattering cross sections for the effects of radiation is considered for experiments in which one of the final-state hadrons is detected in coincidence with the scattered electron. The results are expressed in terms of the missing mass of the unobserved particles.The accuracy of some commonly used approximations is investigated in the case of the ep → epπ⁰ reaction in the region of the Δ (1236) resonance.     

He-HF体系势能模型对散射截面影响的理论研究

用BFW势函数拟合在CCSD(T)/aug-cc-pVQZ理论水平下计算的He-HF相互作用能，获得了He原子与HF分子相互作用的各向异性势，并与其他势模型进行比较，验证了拟合势的可靠性；然后采用量子密耦(Close-Coupling)方法分别计算了He-HF碰撞体系在五种不同势能模型下的微分散射截面、分波散射截面和总截面，并对计算结果进行了详细的比较和分析.研究表明：势能球平均零点能位置、势阱深度、排斥势的强度以及势能在势阱附近的方向性都对散射截面有较大影响. 关键词： 势能模型 密耦方法 散射截面     

He-HI碰撞的转动激发分波截面

基于作者所发展的分子间相互作用势,采用密耦方法计算了入射He原子能量分别为40,75和100　meV时与HI分子碰撞的弹性和非弹性分波截面.研究表明：激发分波截面比弹性分波截面收敛得快;激发态越高,激发分波截面收敛得越快;能量越高,激发分波截面收敛得越慢. 关键词： 分波截面 密耦方法 He-HI复合物     

The energy dependence of nuclear reaction cross sections

The reaction cross section σ_R^pA(E) for proton-nucleus collisions varies with energy as the total cross section σ_t^pN(E) does for proton-nucleon scattering in the energy regime 100 MeV ? E ?400 GeV. We propose several empirical relations, and test them by a χ² analysis of various data. Within the framework of Glauber theory, the parameters in the relations can be linked to the cross section for a single inelastic collision.     

X-ray photoionization cross sections for quantitative analysis

The relative photoemission intensities from subshells of 51 elements and simple compounds have been measured using X-ray photoelectron spectroscopy. The chemical composition of each specimen surface was monitored by Auger electron spectroscopy and contamination was minimized by Ar⁺ ion bombardment. Experimental photoelectron cross sections derived for MgKα (1254 eV) radiation were compared with theoretical Hartree-Slater subshell photoionization cross sections calculated by Scofield. Good correlation (r = 0.96) between theory and experiment was observed over two orders of magnitude for most of the elements studied. Relative cross sections for subshells of a given element are also consistent with theoretical values, with several notable exceptions. The results indicate that quantitative analysis of ESCA spectra is possible using the Scofield cross sections.     

Transport cross sections for excited muonic hydrogen

Transport cross sections for scattering of excited muonic hydrogen on hydrogen are calculated in the quasi-classic approximation in the energy range 0.01–50 eV.     

The fast computation of the compound cross sections

A method is formulated and studied which allows to quickly calculate the fluctuation component of the average cross section for different absorption values in the channels and in the presence of direct inelastic transitions. The experimental data on neutron scattering by^182,184,186W are analyzed.     

Excitation cross sections for a vanadium atom

Moscow Power Engineering Institute, 14 Krasnokazarmennaya Str., Moscow, 105835, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 16–21, November–December, 1995.     

Electron impact excitation cross sections for phosphorus

An analytic atomic independent-particle-model is used to generate wave functions for the valence and excited states of the neutral phosphorus atom. These wave functions are used to calculate generalized oscillator strengths, and from these quantities the cross sections are obtained in Born approximation. Various excitations from the ground state are considered, and results are presented for electron impact energies up to 5 keV. Received: 6 May 1997 / Revised: 21 October 1997 / Accepted: 5 December 1997