K-shell Ionization Probability Research Articles

DirectK-shell ionization probabilities in 30-MeV/u Ne- and 8.3-MeV/u C-induced reactions near zero impact parameter

Direct K-shell ionization probabilities were measured in coincidence with elastically scattered particles in 30-MeV/u $\mathrm{Ne}+\mathrm{Sn},$ Tb, Pb, Th and 8.3-MeV/u $\mathrm{C}+\mathrm{Zr},$ Ag, Sn, Sm, Au, Pb, Th reactions. Experimental data were compared with calculations in the semiclassical approximation. The transitional behavior at the reduced velocity ${\ensuremath{\xi}}_{K}\ensuremath{\approx}1,$ where the projectile velocity approaches the velocity of the K-shell electrons, is discussed.

Time-delay effects on K-shell ionization in the elastic scattering 56Fe(p, p)

The K-shell ionization probability P κ has been measured as a function of E p across the strong 2.534 MeV resonance in the reaction 56Fe(p, p) 56Fe. It varies by about 50%. For the present unprecedentedly large ratio U ϰ / gG ⩾ 5, this experimental result is still in good agreement with theoretical calculations based on Blair and Anholt's formula.

Influence of the recoil effect in Ti K-shell ionization probabilities.

Ti {ital K}-shell ionization probabilities have been measured for {ital p}, {ital d}, and He{sup +} impact at energies of 0.5 MeV/u and at large scattering angles, where the influence of the target-nucleus recoil is most prominent. The data are compared with different semiclassical-approximation calculations including higher-order corrections. Good agreement is only obtained if two-center binding-energy corrections for the adiabatically relaxing state are taken into account.

K- plus L-shell ionization of fourth row elements by 30 MeV/amu Ar ions

Spectra of K X-rays produced by collisions of 30 MeV/amu Ar ions with metallic targets of Ti, V, Cr, Fe, Co, Ni, Cu, and Zn were measured with a Si(Li) detector system. The measured Kα and Kβ transition energies were compared to the results of Dirac-Fock calculations to estimate the average number of L-shell vacancies at the time of K X-ray emission. The target double-to-single K-shell ionization probabilities were also determined, along with the relative probabilities of having single and double K-shell vacancies in the projectile during passage through the metal foils.

Compound nucleus X-ray production across a nuclear resonance in the p + 134Ba reaction

The probability of compound nucleus (CN) and separated atom (SA) X-ray emission in p + 134Ba collisions has been measured as a function of proton energy near the isobaric analog nuclear resonance at 9.295 MeV. X-ray spectra were recorded in coincidence with protons scattered to a mean laboratory angle of 172° and detected by a cooled surface barrier detector which resolved elastically scattered protons from those which ionized one of the target's inner-shell electrons. Our results at five proton energies show good agreement for the predicted K-shell ionization probability ( P K) in the vicinity of this nuclear resonance. The measured ratio of CN to SA K α X-rays is less than 3% integrated over the same region. A slight enhancement of the CN X-ray yield is seen at the resonance energy, and we deduce an upper limit for the peak CN cross section of σ 0 < 4 mb/sr.

K-SHELL ionization induced by 4.5 MeV/u 40Ar ions undergoing fusion reactions

K X-ray spectra of 40 18Ar+ 51 23V, 59 27Co, 62 28Ni fusion evaporation residues are measured in coincidence with γ-rays, protons and α-particles. The spectra are separated into prompt components due to ionization of the target atom by the projectile (PI) and delayed components due to internal conversion of γ-rays deexciting the residues (IC). K-shell ionization probabilities in half-trajectory collisions, P PI 1 2 , are deduced. The results are compared with numerical evaluation of two mechanisms producing K-shell vacancies during the collision: the direct ionization of the target atom by the projectile and the transfer of the K-shell vacancy from the projectile to the K-shell of the united atom. The elemental distribution of cross sections for nuclear reaction products were determined as a by-product from the yields of the PI K X-ray components.

K-shell ionisation probabilities for Co, Cu and Ge by proton impact at large scattering angles

Measurements of K-shell ionisation probabilities of Co, Cu and Ge by proton impact (400-600 keV) have been performed at scattering angles of about 90', 135', and 170'. With the coincidence set-up used it was possible to measure 27 data points within tolerable accelerator run times (10-15 h per data point). The results are compared with various theoretical predictions. The SCA calculations of Kocbach correctly describe the data within experimental errors. It is clearly shown that the influence of the recoiling target nucleus has to be included to obtain agreement between theory and experiment.

The variation of k-shell ionization probability across a narrow p-wave resonance

The projectile energy dependence of K-shell ionization probability have been measured across the narrow resonance 2.522Mev with large ratio of Uk/Γ=5.3 in the reaction 56Fe(p, p) 56Fe. The frame work of the theory proposed by Blair and Anholt was introduced to analyze the results.

THE MODIFICATION OF K-SHELL IONIZATION PROBABILITY THROUGH 2.52 MeV RESONANCE ON 56Fe

This paper presents the experimental result of K-shell ionization probability over 2.52 MeV p-wave narrow resonance in the reaction of 56Fe(P, P0)56Fe. The 50% modification of KX-ray emission probability on resonance relative to off resonance has been clearly observed. It indicates that with the ratio UK/Γ as large as 5.3, the interference between the incoming and outgoing target K-shell ionization amplitudes in an atomic collision still exists. From the comparison of calculation based on theoretical formula of Blair and Anholt with the experimental result. The imaginary part of the atomic monopole amplitude Imb0 was deduced and the R0=Imb0/Reb0 was obtained as +1.8.

Detection of low energy X-rays in coincidence measurements using the organic scintillator NE102A

The organic scintillator NE102A has been used to detect low energy X-rays (6–11 keV) in coincidence measurements of K-shell ionization probabilities. For 500 keV protons on Cu a timing resolution of better than 5 ns has been achieved. The influence of delayed light emission upon detection efficiency has been investigated. It has been found that 25% of the detected pulses are due to delayed light emission if the level of energy discrimination is set slightly above electronic noise. The efficiency of NE102A for undelayed detection of low energy X-rays has been determined by two independent methods.

K-shell ionization probability across a narrow nuclear elastics-wave resonance at 3388 keV in58Ni

TheK-shell ionization probabilityP K was measured at a scattering angle of 95° across the Γ = 2.4 keV nuclear elastic proton resonance in58Ni near 3388 keV. The results are in fair agreement with the theory of Blair and Anholt, especially the splitting of the resonance for the large valueU K /Γ = 3.5 in the coincident channel has been shown. A comparison with recently calculated ionization amplitudes was performed. A remeasurement of the Γ=5.6 keV resonance in58Ni near 3151 keV, originally measured by Blair et al., was found to be in reasonable agreement with the most detailed calculations.

The measurement of impact parameter dependence of K-shell ionization probability by protons

The absolute impact parameter dependence of K-shell ionization probability P( b) has been measured in the impact parameter range 0.03–0.9 pm at incident proton energy of 2 MeV with a Cu target. The ionization cross section of Cu has also been measured at this energy. Good agreement is found between our data and a modified SCA theory and the measured ionization probability was nearly constant at large scattering angles, in good agreement with predictions from SCA calculation with hyperbolic orbit after binding and relativistic corrections.

Time delay effects onKx-ray production probability in deep inelastic U + U and U + Pb nuclear reactions

If an atomic collision is accompanied by a deep inelastic nuclear reaction with a time delay \ensuremath{\Delta}T, a phase change which affects the ionization probability ${P}_{K}$ of the target- and projectile-like products is introduced between the incident and outgoing ionization amplitudes. In a deep inelastic nuclear reaction, the nuclear reaction time \ensuremath{\Delta}T is monotonically related to the total kinetic energy loss (-Q) of the reaction products. Therefore a measurement of ${P}_{K}$ as a function of Q then yields \ensuremath{\Delta}T. The K-shell ionization probability ${P}_{K}$ has been measured in the deep inelastic reactions U + U and U + Pb at a beam energy of 1785 MeV as a function of the total kinetic energy loss -Q. ${P}_{K}$ was determined for Q values down to -190 MeV. After subtraction of the ionization induced by the internal conversion of \ensuremath{\gamma} rays, a strongly Q-dependent ${P}_{K}$ is found, in qualitative agreement with theoretical predictions. From the data we infer a nuclear reaction time of approximately 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}21}$ s at Q=-100 MeV. The observed reaction times agree fairly well with the predictions of the classical nuclear reaction models used to describe deep inelastic scattering processes.

Large resonance effect inK-shell ionization probability in elastic proton backscattering onBa138

We have measured the K-shell ionization probability ${P}_{K}$ at 172\ifmmode^\circ\else\textdegree\fi{} across the 10.00-MeV isobaric analog resonance in the reaction $^{138}\mathrm{Ba}$(p,p${)\mathrm{}}^{138}$Ba. An excursion of more than 200% from the off-resonance ${P}_{K}$ value permits a sensitive comparison with recently calculated atomic-ionization amplitudes. The effects of nonresonant background nuclear scattering and compound-elastic nuclear scattering are considered. The experimental results are found to be consistent with a negligible compound-elastic contribution.

K-shell ionization in the beta decay of 141Ce.

The total K-shell ionization probability accompanying the ${\ensuremath{\beta}}^{\mathrm{\ensuremath{-}}}$ decay of $^{141}\mathrm{Ce}$ to the 0.145-MeV level in $^{141}\mathrm{Pr}$ was determined to be (1.79\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$ from Pr K\ensuremath{\alpha} x rays in coincidence with the 0.145-MeV gamma ray. This result is in very good agreement with the theoretical calculations of Law and Suzuki.

Small impact parameter studies of 2pσ vacancy production in high-Z heavy-ion-atom collisions

K-shell ionisation probabilities were measured for impact parameters between about 10 and 100 fm in collisions between Xe40+ and Sn, Sm, Au and Th. The present data are compared with measurements of ionisation probabilities and total 2p sigma cross sections for other collisions with united-atom atomic numbers up to Zu=184. Also, comparison is made with theories of direct ionisation from the 2p sigma molecular orbital and with a proposed theory involving the two-step transfer of projectile M vacancies into the 2p sigma molecular orbital. The bulk of the high-Z data are in better agreement with the direct ionisation theory.

K-shell ionization by 16O and 32S ions: Reduced-velocity dependence of the binding effect.

K-shell ionization probabilities ${P}_{K}$ were measured for 2.2-MeV/u $^{16}\mathrm{O}$ ions with impact parameter b=16--51 fm on 24 targets ranging from Sc to Bi. For Bi, the distribution ${P}_{K}$(b) was also measured. Total K-shell ionization cross sections ${\ensuremath{\sigma}}_{K}$ for $^{16}\mathrm{O}$ and $^{32}\mathrm{S}$ projectiles are reported for the same target range. Semiclassical calculations using the velocity-dependent electron binding energies from the relativistic two-center approximation of Andersen, Laegsgaard, and Lund reproduce both ${P}_{K}$ and ${\ensuremath{\sigma}}_{K}$ very well, except where polarization effects become important.

K-shell ionization probability in elastic proton scattering on 138Ba through an f7/2 isobaric-analog resonance.

The bombarding energy dependence of the K-shell ionization probability P/sub K/ was measured in elastic proton scattering on /sup 138/Ba at energies near the 69-keV-wide f/sub 7/2/ isobaric-analog resonance at 9.965 MeV. The best simultaneous fit to P/sub K/ in the scattering angle intervals 45/sup 0/--80/sup 0/ and 100/sup 0/--135/sup 0/ yields R/sub 0/ = -0.30 +- 0.30 for the tangent of the phase angle of the semiclassical monopole ionization amplitude.

Comparison of ionisation probabilities in the semiclassical approximation calculated with Rutherford and modified straight-line trajectories

For the collision systems of 15 MeV protons and 50 MeV alphas on 208Pb the authors have calculated the K-shell ionisation probabilities for fixed impact parameters in the semiclassical approximation (SCA) with straight-line trajectories which have been modified according to the procedure of Kocbach (1976). The probabilities agree with those obtained by Trautmann and Baur (1983) who used the SCA with the Rutherford trajectories.

K-shell ionisation in relativistic heavy-ion collisions

For relativistic heavy-ion collisions K-shell ionisation probabilities are calculated in the semiclassical approximation (SCA) and first-order perturbation theory. Most of the results are obtained for a uranium target and show the increasing importance of the spin-dependent interaction potential for relativistic relative velocities nu /c>0.5. Interesting structures arising in certain partial differential ionisation probabilities are discussed.