New effects in the ISR region

We suggest that the increase of total cross sections and large P_T effects observed over the ISR range have a common origin in the hard collision of parton pairs. The observed magnitude of these effects suggest a parton-parton cross section ～ 0.2 mb. The data is consistent with vector gluon exchange mechanisms. These mechanisms can also cause inhibited shrinkage and energy dependent dips in differential cross sections.     

Absolute cross sections for the 6Li(p, 3He)4He reaction at energies below 1 MeV

Total cross sections and angular distributions in the ⁶Li(p,³He)⁴He reaction have been measured over the energy range E_p = 100?700 keV. The extrapolation of the cross section to the energy region which is of interest in controlled thermonuclear reactors is given. The values of the “astrophysical S-function” are deduced from the cross sections.     

Excitation of even configurations of a nickel atom containing nine 3d electrons

The electron-impact excitation of even levels of the nickel atom belonging to configurations that contain nine 3d electrons is studied by the method of extended crossing beams. Ninety-six excitation cross sections are measured at an exciting electron energy of 50 eV. Seven optical excitation functions are recorded in the exciting electron energy range of 0–200 eV. Total excitation cross sections are determined for 24 energy levels of the nickel atom.     

The (γ,2p) reaction on30Si and the (γ,2p), (γ,2pn), (γ,3p) and (γ,3pn) reactions on31P at intermediate energies

The yields of the (γ,2p) reaction on³⁰Si and of the (γ,2p), (γ,2pn), (γ, 3p) and (γ,3pn) reactions on³¹P have been measured as a function of the maximum bremsstrahlung energy in the range 75–640 MeV. The cross sections have been deduced and are compared to Monte-Carlo calculations. The magnitude of the cross sections in the energy range above the threshold for the photoproduction of mesons is also discussed using a simple analytical approach.     

Single and double ionization of neon 2s- and 2p-subshells by proton and electron impact

Absolute single and double ionization cross sections of neon 2s- and 2p-subshells for proton (40–900 keV) and electron impact (0.2–10 keV) have been measured using photon spectroscopy in the spectral range of the vacuum ultraviolet. Cross sections for double ionization decrease more rapidly with increasing impact energy than cross sections for single ionization. No definite asymptotic energy dependence of a Bethe-Fano-plot could be found for double ionization in contrast to single ionization. The experimental results are compared with theoretical predictions of the shake-off model and Gryzinski's classical binary encounter theory. Better agreement is found with the latter, indicating that successive binary collisions have to be considered as a strong mechanism for double ionization by protons or electrons of the investigated energy range. Comparison is made with other experimental results for double ionization by photon impact or capture ionization by proton impact.     

Elastic scattering of electrons by europium and ytterbium atoms

The method of relativistic optical potential is applied to studying elastic scattering of electrons by europium and ytterbium atoms in a wide range of collision energies up to 2 keV. The angular dependences of the scattering differential cross sections and the energy dependences of the scattering integral (total, elastic, momentum transfer, and viscosity) cross sections are calculated in both spin-polarized and spin-unpolarized approximations. It is shown that the spin-polarized approximation should be used to calculate the scattering cross sections at energies below 10 eV for a europium atom. The low-energy scattering of an electron by a europium atom is characterized by P-, D-, and F-wave shape resonances. For an ytterbium atom, the calculated cross sections are in good agreement with available experimental data and with those obtained by calculation in terms of the relativistic convergent close-coupling method.     

Rayleigh scattering fromn=3 states of hydrogenlike atoms

An exact analytic evaluation of the Kramers-Heisenberg matrix elements for Rayleigh scattering fromn=3 states of hydrogenlike atoms is performed in the nonrelativistic dipole approximation, using the Green's function method. The results are given separately for each subshell. The possibility of 3s?3d transitions is also considered. The dependence on the photon energy is contained in six invariant amplitudes. The formulas needed for the evaluation of the various cross sections are presented. The numerical results are contained in tables from which partial and total cross sections can be easily built, covering the energy range from zero up to 20 times theK threshold energy. In the vicinity of Balmerα frequency the cross section is large and comparable with that for excitedn=2 states, confirming an earlier hypothesis of Röhr. At other energies the cross sections forn=2 andn=3 states are comparable, too. The results should be useful in plasma diagnostics.     

Proton Compton effect in the Δ(1232) energy region

The proton Compton effectγ+p→γ+p in theΔ (1232) energy region has been thoroughly studied. At the Bonn 500 MeV synchrotron differential cross sections were measured covering a large range of the CM scattering angle (50°≦θ_γ≦130°) and an energy range from 240 to 440 MeV (LAB energy of the primary photon). A contribution to the counting rate from the competing process ofπ ⁰ photoproduction was strongly suppressed by detecting both particles in the final state and by a proper choice of the endpoint energy of the gamma ray beam. The remaining contribution was monitored experimentally. The measured data were complemented by cross sections at 0° which were computed from the totalγ p cross sections with an input from a multipole analysis of single pion photoproduction. Preliminary results of this experiment have been published in Lett. Nuovo Cimento. In the meantime the experimental data were reanalyzed. The final data presented here are larger than the preliminary ones by about 15%.     

Anionic fragmentation of glycine upon potassium-molecule collisions

In this paper total cross sections (Q _T ) for electron impact on HCl and HBr are reported over a wide energy range from circa 0.1 eV to 2 keV. At impact energies below the ionization energy, the R-Matrix method is employed using Quantemol-N software whilst above the ionization energy the spherical complex optical potential (SCOP) method is used. It is shown that the two methods provide complimentary cross sections where they overlap. These calculations are compared with experimental and theoretical results wherever available.     

Analytically approximate screened calculations of atomic-field pair production cross sections

A new method is described to obtain analytically approximate screened cross sections of atomic-field pair production. The Thomas-Fermi-Csavinszky potential model is expanded at the first order and put in the place of the point Coulomb potential in the Dirac equation. That method can be very useful to calculate approximate screened cross sections for the intermediate photon energy range (5m_oc² to about 50m_oc²) where numerically exact screened cross sections are needing a prohibitive computer time and when the form factor approach based on Born approximation is not always valid.     

Photoneutron cross sections for 9Be obtained with quasi-monoenerget1c photons

Absolute (γ, xn) cross sections for ⁹Be were measured with monochromatic photons from positron annihilation in flight in the energy range from 17 to 37 MeV. No pronounced structure was found in the cross sections in contrast to recent experiments performed with bremsstrahlung sources. The results are compared with many-particle shell model calculations.     

Photoabsorption on nuclei

We calculate the total photoabsorption cross section on nuclei in the energy range from 300 MeV to 1 GeV within the framework of a semi-classical phase space model. Besides medium modifications like Fermi motion and Pauli blocking we focus on the collision broadening of the involved resonances. The resonance contributions to the elementary cross section are fixed by fits to partial wave amplitudes of pion photoproduction. The cross sections for NR → NN, needed for the calculation of collision broadening, are obtained by detailed balance from a fit to NN → NNπ cross sections. We show that a reasonable collision broadening is not able to explain the experimentally observed disappearance of the D₁₃(1520)-resonance in the photoabsorption cross section on nuclei.     

碳对α的非卢瑟福背散射截面研究

报道了散射角为１７０°±１．５°，α粒子能量在５－９．０ＭｅＶ之间，ｃ的背散射截面的实验测量值；用Ｒ矩阵理论，通过与实验数据拟合，分析、给出了一套能级参数，并计算了能量范围在２－９．０ＭｅＶ，ｃ的背散射截面；讨论了对背散射分析感兴趣的窄而孤立的强共振峰４２５０±１０ＫｅＶ随靶厚、角度的变化关系以及截面变化缓慢的平坦区３．６－４．２０ＭｅＶ，６．４２５－６．７００ＭｅＶ能区的截面值与背散射角度的关系。 关键词：     

Inner-shell ionization ofZ=25–32 elements by 5-48 MeV32S ions

TheK-shell ionization cross sections of Mn, Ni, Cu, Zn and Ge under³²S bombardment have been measured in the energy range from 5 to 48 MeV. The cross sections are compared with available theories based on a direct Coulomb ionization mechanism and with the predictions of theK-vacancy sharing process. This last process can reasonably account for the measured cross sections at high bombarding energies. The energy shifts of theK _α- andK _β-lines and theK _α/K _β-intensity ratios have also been measured. This information is used to deduce the defect configuration of the atoms. The mechanisms responsible for the multiple vacancy production are discussed.     

Investigation of spallation reactions on 120Sn and (d, xn), (d, pxn), (p, xn), and (p, pxn) reactions on enriched tin isotopes

The cross sections for (d, xn), (d, pxn), (p, xn), and (p, pxn) reactions on enriched tin isotopes are obtained at a projectile energy of 3.65 GeV per nucleon. The yields in the energy range 0.66–8.1 GeV are analyzed with resort to experimental data obtained previously. Experimental data are compared with the results of theoretical calculations performed within the cascade-evaporation model. The dependence of the yields on the number of emitted neutrons, the projectile type, and the isotopic composition of a target is investigated. The cross sections for the (p, xpyn) reactions on a ¹²⁰Sn target are presented at a primary-proton energy of 0.66 GeV.     

Excitation of the 1s 2- and 1s 4-levels of neon and argon by He+-impact at energies between 100 keV and 1000 keV

The excitation of the 1s ₂- and 1s ₄-levels of neon and argon by He⁺-impact has been studied in the energy range of 100 keV to 1000 keV. The total emission cross sections for the 1s ₂ levels show pronounced maxima at about 350 keV impact energy, whereas the cross sections for the 1s ₄ levels increase with decreasing energy.     

InclusiveΔ ++ inpp interactions at ISR energies

Inclusive cross sections forΔ ⁺⁺ production inpp interactions at different ISR energies are presented. The differential cross sectiondσ/dx forΔ ⁺⁺ production is found to be approximately independent of Feynmanx. No strong energy dependence is seen over the ISR energy range. The topological cross sections ofΔ ⁺⁺ at \(\sqrt s = 62\) GeV show an appreciable contribution from non-diffractive production mechanisms. An upper limit for theΔ ⁰ production cross section is determined.     

A study of the reactions γp→ωp and γp→ωp and γp→ωΔ+

The differential and total corss sections and the decay density matrix elements have been measured for the reactions, γp→ωp and γp→ωΔ⁺ (1232) in the photon energy range 2.8 to 4.8 GeV. The total cross sections for ωΔ⁺ (1232) photo-production are found to be slightly larger than those for elastic ω photo-production in this energy range. The data are compared to the predictions of a theoretical model and the contributing exchange mechanics are discussed.     

Fits to new calculations of photoionization cross sections for low-Z elements

Analytical approximations to results of new calculations of partial (i.e. by subshell) photoionization cross sections of elements (2 < Z < 30, Z = 36) are presented which cover the photon energy range from near threshold to 300 keV. The computer program developed by Brysk and Zerby, which is based on the single-electron model and uses screened self-consistent field and Dirac-Slater wave function data furnished by Cromer, Waber and Liberman, was used. Sufficient multipoles were included to calculate the partial cross sections within a few per cent, on the assumed model. Results for several elements are compared with other calculations and measurements of total photoionization cross sections. The results are presented in a form most convenient for calculations of opacities of hot gases.     

Increasing p-p and p-nucleus cross sections

p-Nucleus cross sections are calculated assuming that total p-p cross sections increase with energy. The dependence on the nucleon structure in b-space is examined and it is found that p-nucleus cross sections grow very rapidly with A if the increasing p-p cross section is attributed to an expanding nucleon halo.