X-ray production by 1.5–11 MeV protons

K-shell ionization andL x-ray production cross-sections by proton impact have been determined from measurements ofK x-ray yields from thin targets of Ti, Fe, Co, Cu, Ni and Ag and ofL x-ray yields from Au and Pb. The proton energies varied from 1.5 to 11 MeV. A Si(Li) semiconductor detector recorded the x-rays. The total error in the measured cross-sections is mostly less than 5%.K _β /K _α ratios andL _l,β,γ /L _α ratios have been determined. Ionization cross-sections have been compared with predictions of the plane-wave Born approximation (PWBA) and the binary-encounter approximation (BEA). Both theories describe the ionization quite well: PWBA is, however, better for higher proton energies whereas BEA is superior for lower energies. An empirical formula for ionization cross-sections is derived.     

Energy dependence of the x-ray production cross sections of Cu and Ag for 150 to 800 keV proton and He+ bombardment

RelativeK-shell x-ray production cross sections have been measured for thin targets of Cu and Ag for proton and He⁺ impact in the energy range 150 to 800 keV. The experimental values are compared to the nonrelativistic plane wave Born approximation (PWBA), the PWBA with corrections for Coulomb deflection and binding effects (PWBABC), and the binary-encounter approximation (BEA). The PWBABC theory provides the best agreement with relative experimental cross sections. For protons, the agreement is within 2% for values of the scaled energy variableγ=η/(εθ)²>0.011; forψ<0.009, however, the deviation reaches about 10%. For helium a 10% deviation appears atγ～0.007. An explanation for these deviations is given.     

Decay asymmetry in non-mesonic weak decay of light Λ -hypernuclei

The proton decay asymmetry, α^NM _p , of the polarized Λ -hypernuclei, ⁵ _ΛHe , ¹² _ΛC and ¹¹ _ΛB , has been investigated to understand the reaction mechanism of the non-mesonic weak-decay process. These Λ -hypernuclei were produced in the highest statistics ever via the (π⁺, K ⁺) reaction at 1.05GeV/c by using the SKS spectrometer at KEK 12GeV PS. The results show that the α^NM _p are very small for these s -shell and p -shell hypernuclei.     

K-shell ionization by protons for Cr, Cu, In and by alpha-particles for Cr, Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.     

Measurement of K β K /α values using proton beamvalues using proton beam

The Measurement of K _β K _/α intensity ratios are measured in some 3d shell elements by using a 2 MeV proton beam along with a high resolution Si(Li) detector. The present Measurement of K _β K _/α intensity ratios are in good agreement with Scofield modified theoretical values, thus supporting the basic assumptions in that theory. From the present Measurement of K _β K _/α intensity ratios, it is evident that due to chemical effects, the experimental Measurement of K _β K _/α intensity ratios will be increased while they will be decreased due to the presence of simultaneous M-shell vacancies which are produced due to proton excitation.     

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.     

Dirac-Hartree-Fock studies of X-ray transitions in meitnerium

The K -shell and L -shell ionizations potentials for ²⁶⁸ ₁₀₉Mt were calculated at the Dirac-Hartree-Fock level taking into account quantum electrodynamic and finite nuclear-size effects. The K _α1 transition energies for different ionization states are accurately predicted and compared with recent experiments in the α -decay of ²⁷² ₁₁₁Rg .     

K-shell excitation spectra of CO,N2 and O2

Electron energy loss spectra of CO, N₂ and O₂ have been recorded in the regions of carbon, nitrogen and oxygen K-shell excitation and ionisation. These results are compared to previous energy loss, photoabsorption and theoretical studies of the same spectral regions. Several inconsistencies in the published spectra are clarified in the present work. Comparisons with recent calculations of the K-shell continua of these molecules are presented. Vibrational structure in the K → π * transitions of CO (C 1s) and N₂ (N 1s) has been resolved in high-resolution studies (< 0.1 eV FWHM) of these species.     

Plane wave born cross sections including exchange forK-shell ionization of light atoms

Cross sections forK-shell ionization by electron impact have been calculated in plane wave Born approximation (PWBA) including outer screening with allowance for electron exchange in Ochkur approximation. The results agree reasonably with available experimental data.     

L-shell vacancy production in Ag,Ta and Au for incident ionsZ 1≦10 in the energy range of 0.125–4 MeV/amu

Absolute Ag, Ta and AuL-shell X-ray cross sections were measured using protons,⁴He,¹⁴N as well as²⁰Ne ions in the energy range of 0.125–4 MeV/amu. By means of single-hole fluorescence yields experimental ionization cross sections were deduced and compared with calculations according to the corrected PWBA model — PWBA(BPCR). With decreasing asymmetry of the collision system the experimental cross sections exceed the predictions of the direct ionization theory. This is caused by an increasing contribution of a competing KL charge exchange mechanism which was investigated in detail for Ne+Ag. The Lapicki and Losonsky capture model was found to fail at energiesE<1 MeV/amu because adiabatic relaxation effects in the projectileK-shell become important. An estimation by means of the Nikitin model led to more physically comprehensible results at the lowest ion velocities investigated.     

Reaction48Ca (p,n)48Sc fromE p =1.885 to 5.1 MeV

The total (p, n) reaction cross section for⁴⁸Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼ 2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The isobaric analogue resonances atE _p ∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorS _n . A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial equilibrium model has also been made.     

Single-particle quadrupole electromagnetic transitions in p-shell and sd-shell nuclei

Electron scattering Coulomb form factors for the single-particle quadrupole transitions in p-shell and sd-shell nuclei have been studied. Core polarization effects are included through a microscopic theory that includes excitations from the core orbits up to higher orbits with 2ω excitations. The modified surface delta interaction is adopted as a residual interaction. The results are discussed for the ( 1p _1/2 ^-1↦1p _3/2 ^-1) proton transition in ¹⁵N, ( 1d _5/2↦2s _1/2) neutron transition in ¹⁷O and ( 1d _3/2 ^-1↦2s _1/2 ^-1) proton transition in ³⁹K. The inclusion of core polarization effects modifies the form factors markedly and describes the experimental data very well in both the absolute strength and the momentum transfer dependence. Received: 18 April 2002 / Accepted: 1 July 2002 / Published online: 6 March 2003 RID="a" ID="a"e-mail: baguniv@uruklink.net Communicated by A. Molinari     

Contribution of the Δ(1232) to the (e, e'p) reaction along with Coulomb distortion effects

The Δ-resonance contribution has been included in the (e, e'p) reaction along with Coulomb distortion effects. We treat the resonance via a non-relativistic Δ current operator and use a Dirac Hartree single-particle model for the ground-state single-particle wave function and a relativistic optical model for the knocked-out proton wave function. It is assumed that the π-meson created by the virtual photon is absorbed in the target nucleus following the production of a Δ-resonance. Our DWBA calculation shows that the Δ-resonance contribution to the (e, e'p) reaction cross-section is 10-15% for an energy of 250 MeV transfered to the proton knocked out of the s-shell of ⁴⁰Ca, in the parallel and perpendicular kinematics. Received: 21 July 2001 / Accepted: 21 March 2002     

Sum peak method applied to the study of decay of Ir-192

The electron capture probabilities to 690.70 and 580.37 keV levels and theK-conversion coefficients of 205.9 and 316.5 keV transitions in the decay of Ir-192 have been determined from the measurement of gamma-ray intensities in conjunction with an analysis of theKX-ray-γ-ray sum peaks observed with a co-axial HPGe detector. TheK-capture probability to 690.70 keV level was determined by an approach which is independent ofK-shell fluorescence yield and absolute detection efficiency forKX-rays. TheK-shell fluorescence yields of the daughter products, namely, Os and Pt of Ir-192 have also been determined by the same technique and were found to be 0.964±0.077 and 0.969±0.068 respectively.     

ΛN Space-exchange effects in thes-shell hypernuclei and Λ 9 Be

Variational Monte Carlo calculations of the ground state separation energiesB _Λ of thes-shell hypernuclei and also of _Λ ⁹ Be have been made for an Urbana-type central space-exchange ΛN potential consistent with Λp scattering, and also including three-body ΛNN forces. Thes-shell hypernuclei are treated asA-body systems (A = baryon number), and _Λ ⁹ Be is analysed as a partially nine-body problem in the Λ — 2α model. The reduction ofB _Λ due to the space-exchange ΛN potential has been calculated for thes-shell hypernuclei for a range of interactions: both ΛN and ΛN + ΛNN forces. ForA = 3,4,5 the exchange energy is approximately, 0.04, 0.15 and 0.50 MeV, respectively. For _Λ ⁹ Be a much more limited study gives ≅ 1.3 MeV. These values are much larger than that for ‘soft’ ΛN +NN potentials when the correlations are weak. Preliminary results were presented at the DAE Symp. on ‘Nuclear Physics’ Vol. 32B (1989).     

K-shell ionization by protons for Cr,Cu, In and by alpha-particles for Cr,Cu

K-shell ionization cross sections have been determined for Cr, Cu and In at proton bombardment in the energy region from 0.9 to 2.5 MeV. The same cross sections were determined for Cr and Cu at alpha bombardment in the 0.9–4.0 MeV region. The experimental results are compared with five different theoretical calculations.     

X-ray converters for radiation treatment of thin films

The energy absorbed in thin films of selected materials bombarded by x rays emitted in the braking of low-energy electrons (E ₀<500 keV) in converters with various atomic numbers (Z=29–73) is calculated by the Monte Carlo method. The program takes into account both of the K-shell ionization mechanisms that lead to emission of characteristic photons as a result of electron impact and as a result of the photoelectric effect, and the characteristic radiation is shown to make a large contribution to the absorbed energy in thin films. Calculations show that the proper choice of material and thickness of the converter affords a two-to fivefold increase in the energy of the x radiation absorbed in thin films of semiconductor materials. Zh. Tekh. Fiz. 68, 99–101 (November 1998)     

K α L 1 satellite multiplet structure of photon-excited chlorine atoms

Summary An attempt is made to study theK _α L ¹ satellite multiplet structure of chlorine atoms in different compounds by photon excitation. A comparison of the averageK _α L ¹ group energy shift from the diagram line with those based on Dirac-Fock evaluations with different number ofM-shell electrons shows a reasonable agreement. The intensity ratios are found to be higher than those studied in Mg compounds in general.     

Inner shell excitation of CH 3F,CH 3Cl,CH 3Br and CH 3I by 2.5 keV electron impact

Small angle inelastic scattering of 2.5 keV electrons was used to study inner shell excitation in the methyl halides at energy transfers between 50 and 700 eV. Discrete peaks due to the excitation of carbon K, fluorine K, chlorine L, bromine M_{4, 5} and iodine N _{4, 5} electrons were observed. Correlations through the methyl halide series were used to aid in the assignment of features in the carbon K-shell spectra. A comparison of halogen inner-shell excitation structures with the carbon K-shell excitation structure in the same molecule allowed a complete assignment of all spectral features. The assignments proposed involve promotions of inner shell electrons to unoccupied valence and Rydberg orbitals. On the basis of our assignments of the chlorine L- and carbon K-shell electron energy loss spectra of CH ₃Cl we propose an alternate assignment of the previously reported CH ₃Cl chlorine K-shell photoabsorption spectrum.     

Recent Result of Muon Catalyzed t–t Fusion at RIKEN-RAL

We have measured X-rays and neutrons associated with the muon catalyzed t–t fusion process at the RIKEN-RAL Muon facility. In the X-ray measurement, we observed K_α and K_β X-rays originating from the muon sticking process in muon catalyzed t–t fusion, and obtained the K_α X-ray yield and the K_β/K_α intensity ratio. An average recoil energy of the (μ⁻α) atoms in a solid T₂ medium was determined from the observed Doppler broadening width of the K_α X-ray line. The obtained t–t fusion neutron has shown an exponential time spectrum with a single component and a continuous energy spectrum with a maximum energy of 9 MeV. We have determined the t–t fusion neutron yield, the t–t fusion cycling rate and the muon sticking probability from the neutron data. The obtained maximum neutron energy is a very peculiar value from the view point of the reaction Q value (11.33 MeV) with the three-particle decay mode at the exit channel: t + t → α + n + n + Q. The obtained neutron energy distribution was analyzed by a simple model with two neutron energy components; reasonable agreement has been obtained, suggesting a strong (n–α) correlation in the exit channel of the t–t muon catalyzed fusion reaction. This revised version was published online in August 2006 with corrections to the Cover Date.