On the energy dependence of inelastic cross sections

The new accurate two-state quantum calculations of the inelastic cross sections in H + Li, Na collisions for energies from the thresholds and till 100 eV or 600 eV are performed, and the results are compared with the Landau-Zener model cross sections in both the diabatic and the adiabatic representations. It is found that the low-energy inelastic cross section is very sensitive to nonadiabatic coupling and, hence, the new NaH coupling is computed. The numerical solutions of the coupled channel equations are checked by independent calculations indicating that the quantum results are accurate. These checks are done by means of the analytic formula for a nonadiabatic transition probability derived within the perturbation approach. Both the Landau-Zener-like and the non-Landau-Zener-like behaviour of the excitation cross sections are found. 34.70.+e Charge transfer     

Scaling of inelastic differential cross sections

Scaling (in the average sense) of differential cross sections is generalised to include inelastic (non-diffractive) reactions. The “derivation” uses, as in earlier work, the Ascoli-Arzelà theorem. Data on π^?p→π⁰n, ηn, over large s and t ranges, are seen to scale very well.     

On the azimuthal dependence of semi-inclusive,deep inelastic electroproduction cross sections

It is pointed out that according to the parton model, there should be no dependence on the azimuthal angle in the cross section for deep inelastic, semi-inclusive electroproduction with one detected hadron in the final state.     

Topological cross sections in proton-proton interactions at 50 GeV

Project Thermalization (Experiment SERP-E-190 at IHEP) is aimed to study the pp interactions at 50 GeV with large number of secondary particles. In this report the experimentally measured topological cross sections have been presented taking into account the detector response and procession effciency. These data are in good agreement with gluon dominance model. The comparison with other models is also made and shows no essential discrepancies.     

Calculations of inelastic cross sections for rotational excitation

Cross sections for scattering of N₂ (j=0) molecules on He atoms have been calculated for relative energies below 5 · 10^?3 eV (58 °K). The time independent scattering formalism ofArthurs andDalgarno was used together with an assumed Lennard-Jones type potential with anisotropicP ₂(cos?) terms in the attractive and repulsive parts. The resulting system of coupled differential equations was solved in the distorted wave and close coupling approximations for the differential and integral cross sections for elastic and inelastic (j=0→j=2) scattering. In the integral inelastic cross section several sharp resonances were found to contribute 40% to the cross section at energies below 40 °K. The resonance peaks are attributed to orbiting or short-lived compound states since they are also observed in the elastic cross section at energies which are lower by the excitation energy of 1.5 · 10^?3 eV. Finally, the effect of varying the potential parameters on the integral inelastic cross section was studied at 50 °K and a rough formula for the cross section as a function of the parameters is obtained. The formula shows that a certain ratio of repulsive and attractive anisotropies leads to a small inelastic cross section indicating a mutual cancellation.     

Calculations of inelastic cross sections for rotational excitation

Cross sections for scattering of N₂ (j=0) molecules on He atoms are calculated for relative energies below the excitation threshold for the N₂ (j=2) rotational state. The close coupling method is used and the coupled differential equations are solved numerically. Very sharp resonances (corresponding to a lifetime of 10^?10 sec) caused by quasistable states of the N₂He system are found in the calculated cross section, when the closed channels corresponding to the N₂ (j=2) states were included in the coupled equations. The position of the resonances is compared with the calculated energy eigenvalues of the corresponding two body potential. Furthermore the equilibrium concentration of the N₂He quasistable and orbiting states is calculated at 80 °K andp _{N 2}=1 Atm. Both concentrations are found to be 1%.     

The relation between channel averages and energy averaged cross sections

For nuclear cross sections a very simple relation between channel averages and averages over incident energy is found. The assumptions used are normally satisfied for sets of channels involved in inclusive cross sections in regions without intermediate structure. In the absence of direct reactions the channel averaged cross sections are expressed in terms of channel averaged transmission coefficients; in the presence of such reactions, channel averages of first and second powers of transmission matrix elements occur when channel correlations induced by direct reactions are neglected.     

Electron-exciton inelastic collision cross sections for different semiconductors

The electron-exciton inelastic collision cross sections for the different semiconductors CdS, ZnO, CdSe, Si, Cu₂O, CuCl, CuBr and CuI have been calculated in the Glauber approximation. The transitions 1s–2s, 1s–3s, 1s–2p and 1s–3p have been considered. The calculations are carried out as function of the different available values of $\text{σ =}\text{m}{}^1{}_{\mathrm{e}}\text{m}{}^1{}_{\mathrm{h}}$ where m¹_e and m¹_h are, respectively, the electron a corresponding semiconductors.     

Magnetic sub-state population cross sections in inelastic alpha-nucleus scattering

Properties of the sub-state population cross sections σ_M for inelastic α-nucleus scattering are explored within the deformed collective nuclear model. The interference between the nuclear and Coulomb parts of the inelastic transition potential is calculated with the DWBA. The effect on the M = ?2 sub-state cross section is substantially more pronounced than that for the usual inelastic differential cross section Σ_mσ_m. The effect of re-orientation terms is calculated by means of a coupled channel formalism for small values of the quadrupole deformation parameter β₂. It is found to shift the angular position of the minima of the σ_M relative to the DWBA result, in a way which depends on the sign of β₂. A spin orbit potential has only a small effect on the σ_M. The calculations refer to 15 MeV α-particles incident on a nucleus of the size and charge of Ca.     

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.     

Coupled-static calculations of the partial and total cross sections of positron-lithium inelastic scattering

The inelastic scattering of positrons by lithium atoms has been investigated in details using a combination of the frozen-core and coupled-static approximations. The ground state of the target has been described by Walters' wave functions. The partial cross sections corresponding to 8 values of the total angular momentuml (0l7) are determined for 21 values of the incident energy lying between 0·1 and 1000 eV. Our results illustrate the stability of the iterative numerical technique employed. They demonstrate the role played by each partial wave in the total cross sections and emphasize the argument that the effect of positronium formation on the total collisional cross sections diminishes when the incident energy is larger than 30 eV.     

Multijet cross sections in deep inelastic scattering at next-to-leading order

We present the perturbative prediction for three-jet production cross section in deep inelastic scattering at the next-to-leading order accuracy. We study the dependence on the renormalization and factorization scales of exclusive three-jet cross section. The perturbative prediction for the three-jet differential distribution as a function of the momentum transfer is compared to the corresponding data obtained by the H1 Collaboration at HERA.     

Direct numerical reconstruction of inelastic cross sections from REELS and ISS spectra

The reconstruction of inelastic scattering cross sections faces two problems: the measured signal (energy spectrum) is a multiple scattering signal; the inelastic energy loss is nonuniform over the target depth. In this paper, we present a method for numerical reconstruction of cross sections from characteristic energy loss spectra, which efficiently solves both problems within a multilayer model. It is shown that the inverse problem of cross section extraction in the three-layer model is ill-conditioned, and the method is practically inapplicable to the three-layer model. The direct numerical reconstruction method yields a strongly “noised” result and can be applied only to obtain a priori information on the inelastic cross section form for further fitting. Using a combination of two methods, inelastic scattering cross sections were reconstructed for aluminum from characteristic energy loss spectra at probe beam energies of 5 and 40 keV. It is shown that ionization in solids should be described as a local process and as a collective one using the dispersion formula similarly to the case of excitation plasmons.     

He-HBr体系各向异性势及非弹性散射截面的理论研究

首先用BFW势函数形式拟合在CCSD(T)/aug-cc-pVQZ理论水平下计算的He-HBr相互作用能数据,得到了He原子与HBr分子各向异性势;并与ESMSV势进行比较,验证了拟合势的可靠性;然后采用公认的精确度较高的CC近似方法计算了He-HBr碰撞体系能量在150meV下He原子和HBr分子碰撞的转动激发微分截面和分波截面,总结了该碰撞体系非弹性散射截面的变化规律.研究表明:①拟合势较好地描述了He-HBr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.②低激发态被激发的几率要远远大于高激发态被激发的几率;激发态越高,大角散射的几率越大.③尾部效应仅在低激发态中产生,高激发态不产生尾部效应.     

Differential cross sections for elastic and inelastic positron scattering from alkali atoms

We have investigated positron scattering from the alkali atoms lithium, sodium, potassium and rubidium, focusing on the calculation of differential cross sections for elastic scattering and impact excitation. The results obtained with the two-state and five-state close-coupling method as well as the first-order distorted wave Born approximation are compared with each other and with some selected results for electron scattering. Numerical problems due to lack of, or numerically inaccurate, calculation of partial waves with large angular momenta are solved through semi-empirical fitting/extrapolation procedures.     

Maximal electromagnetic contribution to pp inelastic cross sections at ISR energies

The maximal electromagnetix contribution to the pp inelastic cross section is estimated. Although this contribution is insufficient in itself to explain all of the recently observed rise at ISR energies if the purely strong cross section is asymptotically constant, it could amount to as much as approximately 3 mb at √s ≈ 53 GeV if the purely strong cross section rises with energy through the range of present accelerator energies like (ln s)² or slower.     

Charged particle multiplicities and inelastic cross sections in high energy nuclear collisions

Inelastic cross sections at 60 and 200 GeV/nucleon are determined in a streamer chamber for ¹⁶O on several nuclear targets. Charged particle multiplicity distributions for inelastic and central collisions are studied and compared with theoretical predictions. The inelastic cross section exhibit a geometrical dependence on nuclear radii. The multiplicity data are governed by the collision geometry. They are consistent with a picture of superposition of independent nucleon-nucleus interactions.     

Strange particle cross sections and multiplicity distributions in 19 GeV/c proton-proton interactions

Inclusive cross sections are presented for strange-particle production in proton-proton interactions at 19 GeV/c for the pairs $\text{(}\text{K}{}^0\text{K}{}^0{}_{\mathrm{C=+1}}\text{,}\text{K}{}^0\text{Λ,}\text{K}{}^{\mathrm{+}}\text{Λ,}\text{K}{}^0\text{Σ}{}^{\mathrm{+}}\text{,}\text{K}{}^0\text{Σ}{}^{\mathrm{?}}$ and for Λ, K_s⁰, Σ⁺, Σ^? and Ξ^?. The $\text{K}\text{K}$, the KY and the total strange particle cross sections have been found to be 1.40 ± 0.10 mb, 2.69 ± 0.09 mb and 4.23 ± 0.20 mb, respectively. The charged multiplicity distributions for events with K_s⁰, Λ, $\text{(}\text{K}{}^0\text{K}{}^0\text{)}{}_{\mathrm{C=+1}}$ or K⁰ Λ are shown to follow a modified KNO curve, whereas K⁺ Λ does not. For the inclusive reactions $\text{pp}\text{→(}\text{K}{}^0\text{K}{}^0\text{)}{}_{\mathrm{C=+1}}\text{+}\text{X}{}^{\mathrm{++}}\text{,}\text{pp}\text{→}\text{K}{}^0\text{Λ +}\text{X}{}^{\mathrm{++}}\text{and pp}\text{→ Λ +}\text{X}{}^{\mathrm{++}}$, we find that the average charged multiplicity of the remainder system X⁺⁺ is the same as when X⁺⁺ is produced in other reactions with the same system energy and quantum numbers.     

Supernova inelastic neutrino-nucleus cross sections from high-resolution electron scattering experiments and shell-model calculations

Highly precise data on the magnetic dipole strength distributions from the Darmstadt electron linear accelerator for the nuclei 50Ti, 52Cr, and 54Fe are dominated by isovector Gamow-Teller-like contributions and can therefore be translated into inelastic total and differential neutral-current neutrino-nucleus cross sections at supernova neutrino energies. The results agree well with large-scale shell-model calculations, validating this model.