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.     

Inner-shell ionization by relativistic electron impact

K-, L andM-shell ionization cross sections have been measured for 23 elements, 12≦Z≦92, after bombardment with relativistic electrons, 15≦E ₀65MeV, by means of high resolution semiconductor detectors and a recently developed gas-scintillation proportional counter. For constant electron bombarding energyE ₀ the ionization cross sections follow a power law dependence,σ∽Z ^?α, and forE ₀=50MeV we deducedα =2.45±0.02 for theK shell andα=3.00 ±0.09 for theL shell. The observedZ dependence exhibits significant systematic deviations from theoretical predictions which exceed the experimental values up to 15 % at lowZ elements for theK shell and on the average about 11% for theL andM shell. The same behaviour of too low experimental values, i.e. an overestimation by the theory, is observed for the energy dependence of the cross sections for all shells. A scaling behaviour describing theZ andE ₀ dependence for allK-, L andM-shell data points is observed which also predicts the experimental values by other groups at lower and higher energies correctly. The comparsion of the measuredLΒ/Lα, andLγ/Lα intensity ratios for highZ elements with the values obtained by other groups in the energy range 0.3≦E₀≦1,000 MeV exhibits an increase with bombarding energy that cannot merely be explained by the energy dependence of the subshellionization cross sections for theL shell. An attempt to explain this effect with the change of the Coster-Kronig transition probability is described.     

Analysis of the3 He(K−,K +)n reaction by the potential quark model

We analyze the production of H dihyperson (J ^π=0⁺,S=?2) via the (K ^?, K⁺) reaction by means of the non-relativistic quark model. First, the H mass and mass spectrum of single baryons are calculated. When the single baryon spectrum is well reproduced, the H dihyperson has the binding energies about 20 MeV or 60 MeV corresponding to the choice of the strength of the confinement potential. Using this model and parameters, cross sections for H production are estimated. A new effect, contributions from color-octetQ ³?Q ³ components of H dihyperson, is taken into account. The cross sections for H production are enhanced about ten times by these contributions. TheK ⁺-neutron coincidence cross section for H production is found to be 99–115 nb/sr² at theK ⁺ forward direction forM _H=2212 MeV and theK ^? beam momentum 1.8 GeV/c.     

Search for the density effect in inner-shell lonization by ultra relativistic electron impact

We have extended the measurements ofK-andL-shell ionization cross sections by electron impact into the ultra relativistic energy region, 0.9≦E≦2.0 GeV, in order to search for a saturation of the cross section. This phenomenon, which is due to the polarization of the target medium, is called density effect. It is predicted to occur at several hundred MeV impact energy and preferentially for lowZ target elements. Theoretical calculations are presented, based on the one-photon-exchange approximation. The absolute measurements of theK-andL-shell cross sections for Ni(K), Cu(K), Ag(K, L) and Au(L) performed at the 2.5 GeV electron synchrotron of the Bonn University, however, exhibit that the cross sections show no saturation but are still increasing. Furthermore, from theK X-ray yields, obtained at 0.9 and 2.0 GeV by bombarding the lowZ elements S, Ca, Mn, Ni and Ge, we obtain for the corresponding cross section ratio σ _K (2GeV)/σ _K (0.9GeV)=1.08±0.01 on the average. TheK X-ray yield of a composite Ca — Mn target amounts to $$[\sigma _K (Ca;2.0GeV)/\sigma _K (Mn;2.0GeV)]/[\sigma _K (Ca;0.9GeV/\sigma _K (Mn;0.9GeV)] = 0.99 \pm 0.02.$$ . All three results are in disagreement with theory. This severe discrepancy is discussed but the origin for it is not yet understood.     

K-shell ionization of Si,Ti, Cu and Ag for incident protons,4He and14N ions in the energy range of 0.17–2.0 MeV/amu

K-shell X-ray production cross sections of Si, Ti, Cu and Ag were measured for incident protons,⁴He and¹⁴N ions in the energy range of 0.17≦E ₁/A ₁≦2 MeV/amu. The experimental ionization cross sections are compared with calculations according to the simple Plane Wave Born Approximation (PWBA) theory as well as the corrected PWBA model (PWBABC). Strong deviations of the experimental cross sections from theZ ₂ ¹ scaling are observed and discussed quantitatively.     

Measurements of double differential cross sections in electron impact ionization of helium and argon

Double differential cross sections (angular distributions and energy loss spectra) have been measured of electrons after ionizing electron collisions with helium at primary energiesE ₀ between 25 eV and about 260 eV and with argon atE ₀=75, 150 and 200 eV. The spectra have been measured with an energy analyzing collector system of constant transmission. It was found that for high collision energies (E ₀≧ 80 eV) the outgoing electrons belong to one of the two energetically well separated groups, either thefast electrons, which are scattered mainly in forward direction or theslow electrons which are distributed isotropically into all angles. At low primary energiesE ₀ no separation into groups is possible. Several findings indicate the qualitative applicability of the binary collision model.     

Measurements ofK-shell ionization with132Xe and208Pb projectiles in the energy range of 1.4–5.9 MeV/u

Projectile and targetK-shell ionization cross sections induced by 3.6-, 4.7-, and 5.9 MeV/u¹³²Xe ions and 1.4-, 3.6-, 4.7-, and 5.9 MeV/u²⁰⁸Pb ions from the UNILAC in thin solid targets between C and U are measured. The cross sections are discussed in terms of the molecular model of innershell vacancy production in heavy ion-atom collisions. The sharing of 2p _1/2σ vacancies between theK shells of the two collision partners in these very heavy ion-atom collisions is found to deviate from the Meyerhof-Demkov formula forR≦10^?2. The measured ionization cross sections are compared with theoretical calculations for 1sσ and 2p _1/2σ excitation cross sections. AZ _UA=Z₁+Z ₂ dependence is found independent ofZ ₁/Z ₂. Outer-shell vacancy configurations measured in these close encounters are reported.     

Auger- und Coster-Kronig-Übergänge der M-Schale von Krypton

The Auger spectra of theM ₂,M ₃,M ₄,M ₅ subshells of krypton and the Coster-Kronig spectra of theM ₁,M ₂,M ₃ subshells of krypton were measured with an electrostatical spectrometer. The ionization in theM shells was caused by electron impact. The use of a gaseous target made it possible to measure the Auger lines even at energies as low as 25 eV. The absolute energies and relative intensities of a great number of transitions were determined: 22 of theM _{4, 5} spectrum, 14 of theM _{2, 3} spectrum and 2 of theM ₁ spectrum. Only in the case of theM _{2, 3} spectrum a comparison between the relative intensities, determined experimentally, and those calculated byRubenstein forZ=47 was possible. The agreement is only qualitatively. Moreover, from the Auger electron energies measured, the following binding energies were calculated:E(M ₁)=(292,1±1,0) eV,E(M ₂)=(222,1±0,6) eV,E(M ₃)=(214,6±0,6)eV,E(N ₁ N ₁)=(62,81±0,05) eV.     

A study of elastic photoproduction of low massK + K − pairs from hydrogen in the energy range 2.8–4.8 GeV

The results of an experiment to study elasticK ⁺ K ^? photoproduction are presented. Differential cross sections and spin density matrix elements for ?(1.019) production are stddied as a function of incident photon energy and over a wide range of momentum transfer,t (t _min >t>?1.5(GeV/c)²). Helicity conserving amplitudes are observed to dominate ? production throughout this range and the differential cross sections exhibit a forward diffractive peak which cannot be understood in terms of a simple exponential dependence. A new value of the photon ? coupling constant is determined and shown to be consistent withe ⁺ e ^? annihilation measurements. A detailed study of the energy dependence of the differential cross sections is made, including other experimental data, and the extracted effective Regge trajectory compared with other diffractive processes. A study of the dependence of theK ⁺ K ^? decay angular distribution on invariant mass reveals evidence for ans wave contribution interfering with thep wave ? which may be attributable to theS ^* meson.     

K-shell X-ray production for fluorine ions on target elements Ti to La

The production of target atomK-shell X-rays has been studied for 2 to 28 MeV fluorine ions incident on thin solid targets of 14 elements with atomic numbers Z₂=22 to 57. Total X-ray production cross sections, energy shifts ofK _α andK _β lines andK _α/K _β intensity ratios were measured with a Si(Li) detector. The results of cross section measurements are compared with theoretical predictions of inner shell ionization. In most cases, satisfactory agreement between measured cross sections and theoretical Coulomb ionization cross sections, corrected for the perturbation of the target atom by the projectile charge and for relativistic effects, was obtained.     

Oxygen inducedK-shell ionization of selected elements from sulphur to bromine

K-shell X-ray production cross sections for oxygen ions on thin solid targets of 13 selected elements with atomic numbers between 16 and 35 were measured by a Si(Li) detector at incident ion energies from 7 to 24 MeV. Ionization cross sections are compared with calculations assuming Coulomb-ionization. Best agreement is found with theoretical cross sections that include corrections for binding energy and Coulomb deflection effects. Energy shifts ofK _α andK _β X-rays andK _α /K _β intensity ratios were also measured and are used to deduce information about outer shell ionization.     

Application of atom-photon coincidence techniques to the determination of the differential cross section for excitation ofK(42 P) in low-energy K-N2, CO collisions

The differential cross section for the processK(4² S)+N₂, CO→K(4² P)+ N₂, CO is presented for reduced scattering angles τ<2·10⁴ eV deg. The inelastic process is identified by determining the time-correlation between the inelastically scattered potassium atom and the emittedK(4² P→4² S)photon. The performance of different coincidence techniques is compared. From the differential cross sections values for the position of the curve crossing responsible for the excitation process are derived (R _c=2.77, 2.48 Å andV(R _c )=0.55, 1.00 eV for K-N₂, CO respectively). The values indicate that the lowest ionic intermediate state of the form K⁺-N ₂ ^? , CO^? is responsible for the excitation process.     

Effect of hyperon channels in low-energyK − d scattering

Within the framework of a Faddeev formalism and an implicit hyperon channel approximation, we have calculatedK ^? d elastic, total, and reaction cross sections for incident kaon laboratory momenta up to 120 Mev/c. We have used as input two different (slightly modified) multichannelM matrix fits to low-energy¯KN scattering, each of which contains explicitly theπ Y channels, as well as a single channel representation of the¯KN interaction in which the hyperon channels appear only through their contributions to the imaginary parts of the¯KN scattering lengths. TheK ^? d cross sections obtained with the single channel¯KN input differ by only some 10% from those for which we used the multichannel¯KN input. TheK ^? d cross sections calculated using¯KN input parameters from each of the two separateM matrix fits differ across the entire momentum range investigated by 25–35%.     

Dynamical treatment of binding,polarization and recoil in asymmetric ion-atom collisions

The cross sections for quenching the lowestn ² P states of the alkali atoms Li, Na, K., and Rb by the inert gases He, Ne, Ar, Kr, and Xe are presented for 5 eV≦E _c.m.≦ 100 eV. These cross sections are derived from the corresponding cross sections for collisional excitation by applying the principle of microreversibility. Upper estimates for the quenching cross sections at thermal energies are given; in all studied cases the quenching cross sections are <8·10^?3Ų. These new upper limits are in most cases much lower than those obtained from other methods previously.     

InclusiveK *+(890),K *+(1430) and\bar K^{ * - } (890) production inK + p interactions at 32 GeV/c

We present final results on inclusive production ofK ^*+(890),K ^*+(1430) andK ^*?(890) in \(\bar K^ + p\) interactions at 32 GeV/c, based on a statistics of ～27 events/μb. Total cross sections,p _T -andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK ^*+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks \(\bar s\) andu of theK ⁺ intoK ^*+(890), responsible in the Lund model for ～45% of theK ^*+(890) cross section, is strongly suppressed.     

InclusiveK *+(892) andK *0(892) production inK + p interactions at 32 GeV/c

Total and semi-inclusive cross sections, longitudinal and transverse momentum distributions and spin density matrix elements of theK ^*+(892) andK ^*0(892) produced in the inclusive reactionsK ⁺ p→K ^*+(892)+X andK ⁺ p→K ^*0(892)+X at 32 GeV/c are studied in detail. The inclusive spectra of theK ^*(892) and their decay products are compared with pion and neutral kaon production. TheK ^*+(892) andK ^*+(892) are dominantly produced by kaon fragmentation processes. The dependence of average transverse momentum <p _T> vs.x for resonances has been investigated for the first time.     

Total toK-shell photoelectric cross section ratios in Zr,Ag, Ta,and Th

Total photon atomic cross sections in elements Zr, Ag, Ta and Th were determined around theirK-edges in the energy region 6 to 400 keV with a good geometry set-up using proportional counter or Ge(Li) detector system. From these values the photoelectric cross sections were obtained by subtracting the theoretical values of coherent and incoherent scattering cross sections. The resulting photoelectric cross sections were fitted to curves above and below theK-edge for each element and extrapolated on either side and the total toK-shell photoelectric cross section ratios were determined with an error not exceeding 2%. The ratios were compared with the theoretical values obtained by Grodstein and others, as also from the empirical relation of Hubbell. The present values show good agreement with those of Scofield. A definite trend of decrease of the ratio as the energy increases is observed in the case of Th unlike in the previous experimental studies.     

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 - andK -lines and theK /K -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.     

Meson-baryon scattering with SU (3) invariant interactions

The static model invariant under SU₃ is discussed. The baryons and mesons are assigned according to the “eightfold way”, and the Low equation for the scattering matrix is derived. The scattering matric has been diagonalized for arbitrary mixing ofF- andD-type coupling and the crossing matrix has been calculated. To determine the mixing of the two couplings photoproduction cross sections have been calculated. From the comparison of theK ⁺ Λ andK ⁺ Σ0 production cross sections with experiment it follows that α=D/F=3.5. For this value of α the model predicts the 3/2 decublet resonance in very good agreement with the experimental situation.     

Study of cross sections for the loss of outer 1s, 2s, and 2p electrons by fast ions and atoms of light elements

In the case of light-element ions propagating with velocities V = 1.83 and 3.65 au in H₂, He, N₂, Ne, and Ar, the loss cross sections σ_{i, i+m} for m electrons (m = 1, 2, 3) are considered. The partial loss cross sections σ_i(nl) for one of the outer 1s, 2s, or 2p electrons are determined using the obtained data. It is shown that the experimental cross sections for the loss of the 1s and 2s electrons by positive ions qualitatively agree with the theoretical values calculated in the Born approximation. In the case of the ion velocity V = 1.83 au, the cross sections σ_i for 2p electrons are greater than the cross sections σ_i (1s) and σ_i (2s) by a factor of 1.2–3 for the same binding energies of electrons in the ion (I _nl > 20 eV). It is found experimentally that, at V = 1.83 au, the cross sections σ_i (2p) for I _nl ～ 10–20 eV are less than the cross sections σ_i (1s) by a factor of 2–3, which is probably caused by a decrease in the screening parameter (θ_2p < 1) of the outer shell of atoms.