K-shell Electron Capture Research Articles

Results of In-Depth Analysis of Data Obtained in the Experimental Search for 2K(2ν)-Capture in 78Kr

A brief description of the results of joint analysis of data obtained in long-term measurements of krypton samples differing in 78Kr content is presented. Low-background high-pressure proportional gas counters were used as detectors. The comparative analysis of experimental data on single and double K-capture provided the first estimate of the probability of production of a double K-shell vacancy in the process of K-shell electron capture in 81Kr: $${{P}_{{KK}}} = \left[ {5.7 \pm 0.8\,\,({\text{stat}}{\text{.}}) \pm 0.4\,\,({\text{syst}}{\text{.}})} \right] \times {{10}^{{ - 5}}}$$ . A new result for the half-life of 78Kr with respect to the 2K(2ν)-mode was also obtained: $${{T}_{{1/2}}} = \left[ {1.9_{{ - 0.7}}^{{ + 1.3}}\,\,({\text{stat}}{\text{.}}) \pm 0.3\,\,({\text{syst}}{\text{.}})} \right] \times {{10}^{{22}}}$$ years (90% CL).

Capture of K-shell electrons by α-particles in α-decay of superheavy nuclei: I. Charge transfer in collisions of α-particles with He+(1s) ions

We consider a process in which α-particles after α-decay ionize K-shell of daughter atoms and capture electrons. We first have performed similar calculations for collisions of α-particles with He+(1s) ions. This charge transfer process is studied for the collision energy region 0.04–400 keV. The transition amplitudes are calculated in the impact parameter approximation with the use of the close coupling equations method for a basis consisting of eight molecular states. Total and partial charge-transfer cross sections to the 1s and, for the first time, to the 2s and 2p 0, 2p ±1 states of the He+ ion are obtained. Angular differential cross sections for the elastic scattering and charge-transfer processes are calculated in the eikonal approximation for a wide range of scattering angles for the collision energy of 1 keV. Results of calculations are in an excellent agreement with experimental data.

Inner-shell electron capture by impact of positron on the multi-electron atomic targets

The first-order Coulomb-Born approximation has been applied to the study of positronium formation through K-shell electron capture in the collision of positron with multi-electron atomic targets. The single-zeta Roothaan-Hartree-Fock wave functions are used to describe the electron initial bound states. The differential and total cross sections are computed for the impact of positron on helium, carbon, neon, sodium and argon atoms, with the formation of positronium in its ground state. For helium atoms, the calculated total cross sections are compared with the available experimental data and other theoretical calculations. The comparison shows a good agreement between the present calculations and the measurements.

Comment on “Time Modulation of theK-Shell Electron Capture Decay Rates of H-like Heavy Ions at GSI Experiments”

According to GSI experiment Phys.Lett.B 664, 162 (2008), the rate of the daughter ion production by the K-shell electron capture (with neutrino emission) in H-like ions 142Pm, 140Pr and 152I is modulated with a period of 6 to 7 seconds. In PRL 103, 062502, 2009 by Ivanov and Kienle (also by Lipkin}) there is a claim that neutrino oscillations may explain this result. In arXiv:0811.2302 by Lambiase et al a different explanation is suggested which is based on the rotation of electron and nuclear spins. The aim of this Comment is to show why these explanations are not satisfactory and to discuss other possibilities.

Ivanov and Kienle Reply:

According to experimental data at GSI, the rates of the number of daughter ions, produced by the nuclear K-shell electron capture (EC) decays of the H-like 140Pr58+, 142Pm60+ and 122I52+ ions, are modulated in time with periods T_{EC} of the order of a few seconds, obeying an A-scaling T_{EC} = A/20 s, where A is the mass number of the mother nuclei, and with amplitudes a^{EC}_d ~ 0.21. In turn, the positron decay mode of the H-like 142Pm60+ ions showed no time modulation of the decay rates. As has been shown in Phys. Rev. Lett. 103, 062502 (2009) and Phys. Rev. Lett. 101, 182501 (2008), these data can be explained by the interference of two neutrino mass-eigenstates. In this letter we give a reply on the comments on our paper Phys. Rev. Lett. 103, 062502 (2009) by V. Flambaum (arXiv: 0908.2039 [nucl-th]).

The influence of the magnetic field of the GSI experimental storage ring on the time-modulation of the EC-decay rates of the H-like mother ions

We investigate the influence of the magnetic field of the experimental storage ring (ESR) at GSI on the periodic time dependence of the orbital K-shell electron capture decay (EC) rates of the H-like heavy ions. We approximate the magnetic field of the ESR by a homogeneous magnetic field. Unlike the assertion by Lambiase et al (2008; arXiv:0811.2302 [nucl-th]), we show that the motion of a H-like heavy ion in a homogeneous magnetic field cannot be the origin of the periodic time dependence of the EC-decay rates of the H-like heavy ions.

On “GSI Oscillations” as Interference of Two Closely Spaced Ground Mass Eigenstates of H-Like Mother Ions

We analyse the hypothesis that the “GSI oscillations” of the K-shell electron capture decay (EC) rates of the H-like heavy ions are caused by quantum beats from a coherent state of two closely spaced ground mass-eigenstates and of decaying H-like heavy ions. We apply this mechanism to the calculation of the -decay rates of the H-like heavy ions and discuss the dynamics of the production of the H-like heavy ions with two closely spaced ground mass-eigenstates at GSI experiments. We show that such a mechanism cannot describe simultaneously the experimental data on both the EC-decay and -decay rates of the H-like heavy ions, measured at GSI.

Time Modulation of theβ+-Decay Rate of H-LikePr58+140Ions

Recent experimental data at GSI on the rates of the number of daughter ions, produced by the nuclear K-shell electron capture (EC) decays of the H-like ions 140Pr58+ and 142Pm60+, suggest that they are modulated in time with periods T_{EC} approximately 7 sec and amplitudes a_{EC} approximately 0.20. Since it is known that these ions are unstable also under the nuclear positron (beta;{+}) decays, we study a possible time dependence of the nuclear beta;{+}-decay rate of the H-like 140Pr58+ ion. We show that the time dependence of the beta;{+}-decay rate of the H-like 140Pr58+ ion as well as any H-like heavy ions cannot be observed.

Weak decays of H-like140Pr58+and He-like140Pr57+ions

The nuclear K-shell electron-capture (EC) and positron ({beta}{sup +}) decay constants, {lambda}{sub EC} and {lambda}{sub {beta}{sup +}} of H-like {sup 140}Pr{sup 58+} and He-like {sup 140}Pr{sup 57+} ions, measured recently in the experimental storage ring (ESR) at GSI, were calculated using standard weak interaction theory. The calculated ratios R={lambda}{sub EC}/{lambda}{sub {beta}{sup +}} of the decay constants agree with the experimental values within an accuracy better than 3%.

Polarization studies on the radiative recombination of highly charged bare ions

The polarization of the emitted photons is studied for the radiative recombination of free electrons into the bound states of bare, highly charged ions. We apply density matrix theory in order to investigate how the photon polarization is affected if the incident electrons are themselves spin polarized. For K-shell electron capture, for instance, the linear polarization of the light, which is measured out of the reaction plane, is defined by the degree of polarization of the electrons and may be used as a tool for studying the polarization properties of the electron targets and/or the projectile ions. Detailed computations of the Stokes parameters of x-ray emission following the radiative recombination of bare uranium ions ${\mathrm{U}}^{92+}$ are carried out for a wide range of projectile energies and for different polarization states of the incident electrons.

Effect of host medium on theL/Kratio in7Beelectron capture

We discuss in the framework of linear muffin-tin orbital method and Bahcall's calculations how the ratio of L- to K-shell electron capture rates $(L/K$ ratio) in ${}^{7}\mathrm{Be}$ would be affected by the host medium in which ${}^{7}\mathrm{Be}$ is implanted. Our calculations show that the recently observed discrepancy between the measured and observed $L/K$ ratio in ${}^{7}\mathrm{Be}$ could be understood quantitatively as a result of in-medium effects distorting the L-shell electron orbital of ${}^{7}\mathrm{Be}.$

00/00007 Low-temperature oxidation of coal studied using wire-mesh reactors with body steady-state and transient methods

Gamma-ray and Kα X-ray emissions have been measured from a very pure 209Po source containing less than 0.13% 208Po activity and no detectable 210Po (≤ 2 × 10−4%). The alpha-particle emission rate for this source has previously been determined. Data are presented that confirm alpha decay to the 205Pb excited level at 262.8 keV, with an alpha-particle emission probability (±standard uncertainty) of 0.00559±0.00008. The ratio of K-shell electron capture to total electron capture for the second forbidden unique electron capture decay to the 896.6 keV level in 209Bi was determined to be 0.594±0.018. The electron capture decay fraction was found to be 0.00454±0.00007, while the probabilities per decay for the 896.6, 262.8, and 260.5 keV gamma rays and the Bi Kα and Pb Kα X-rays were measured as 0.00445±0.00007, 0.00085±0.00002, 0.00254±0.00003, 0.00202±0.00005, and 0.00136±0.00005, respectively.

Charge state dependence of L-shell X-ray production cross sections of 28Ni, 29Cu, 30Zn, 31Ga and 32Ge by 12 MeV 16Oq+ ions

L-shell X-ray production cross sections of elements from Z2=28 to 32 were measured. A 12 MeV incident oxygen beam, with and without K-shell vacancies, was used to make a charge state dependence analysis. Simultaneous measurements were made of both scattered particles and X-rays from the ultra-clean foils that had been made sufficiently thin to reach the single-collision regime. Target L-shell to projectile K-shell electron capture for hydrogen-like (q=Z1−1) and fully stripped (q=Z1) oxygen ions were then extracted. The measurements are compared with the predictions of the ECPSSR theory using a single-hole fluorescence yield. In general and contrast to the first Born calculations, this theory gives reasonable agreement with the data for oxygen ions without K vacancies. However, the ECPSSR still significantly overpredicts the data for oxygen ions with K vacancies.

Alpha-particle and electron capture decay of 209Po

Gamma-ray and Kα X-ray emissions have been measured from a very pure 209Po source containing less than 0.13% 208Po activity and no detectable 210Po (≤ 2 × 10 −4%). The alpha-particle emission rate for this source has previously been determined. Data are presented that confirm alpha decay to the 205Pb excited level at 262.8 keV, with an alpha-particle emission probability (±standard uncertainty) of 0.00559±0.00008. The ratio of K-shell electron capture to total electron capture for the second forbidden unique electron capture decay to the 896.6 keV level in 209Bi was determined to be 0.594±0.018. The electron capture decay fraction was found to be 0.00454±0.00007, while the probabilities per decay for the 896.6, 262.8, and 260.5 keV gamma rays and the Bi Kα and Pb Kα X-rays were measured as 0.00445±0.00007, 0.00085±0.00002, 0.00254±0.00003, 0.00202±0.00005, and 0.00136±0.00005, respectively.

High-resolution study of electron capture by 72- and 52-MeV 3He projectiles from targets of high atomic number.

An electron capture at the cyclotron energy has been explored by using a high-resolution magnetic spectrograph. The K-shell electron capture from heavy elements (V, Cr, Cu, Ge, Nb, Ag, and Sn) by $^{3}\mathrm{He}^{2+}$ projectiles at 52 and 72 MeV was measured. The dependence of the cross sections on the atomic number of the target obtained at these two energies are compared with current electron-capture theories. \textcopyright{} 1996 The American Physical Society.

K-shell electron capture from negative ions

Electron capture from the K-shell of a negative ion by protons is considered by accounting for the interplay between the final channel-distorted projectile and off-shell electronic scattering motions using the distorted strong-potential Born approximation. The distorted motion accounts for the ionized state of the target core and the short-range shielding of the K-shell by the passive outer-shell electrons. Total cross sections versus incident energy are compared for the negative-ion, neutral, and singly-ionized forms of the second- and third-row elements C, O, F and Si, S, Cl. Target core neutrality and diffuseness of the negative-ion screening consistently lower the cross section by amounts ranging from 22 to 37% while the positive-ion results are larger by only 1 to 15%. Previous comparison with experiment and coupled-Sturmian-pseudostate results for neutrals has shown very good agreement.

Coral grief: K. Muzik, Technology Review, 94(3), 1991, pp 60–67

Gamma-ray and Kα X-ray emissions have been measured from a very pure 209Po source containing less than 0.13% 208Po activity and no detectable 210Po (≤ 2 × 10−4%). The alpha-particle emission rate for this source has previously been determined. Data are presented that confirm alpha decay to the 205Pb excited level at 262.8 keV, with an alpha-particle emission probability (±standard uncertainty) of 0.00559±0.00008. The ratio of K-shell electron capture to total electron capture for the second forbidden unique electron capture decay to the 896.6 keV level in 209Bi was determined to be 0.594±0.018. The electron capture decay fraction was found to be 0.00454±0.00007, while the probabilities per decay for the 896.6, 262.8, and 260.5 keV gamma rays and the Bi Kα and Pb Kα X-rays were measured as 0.00445±0.00007, 0.00085±0.00002, 0.00254±0.00003, 0.00202±0.00005, and 0.00136±0.00005, respectively.

Double K-shell vacancy production in the electron capture decay of 139Ce.

The probability of double K-shell vacancy production in the electron capture decay of $^{139}\mathrm{Ce}$ to the 166-keV level of $^{139}\mathrm{La}$ has been investigated. Triple coincidences between the 166-keV gamma ray, the La satellite K\ensuremath{\alpha} x ray, and the La hypersatellite K\ensuremath{\alpha} x ray were measured using two intrinsic Ge detectors. We looked for the sum of two of the three radiations in one detector in coincidence with the third radiation in the other detector. The probability of double K-shell vacancy production per K-shell electron capture (${\mathit{P}}_{\mathit{K}\mathit{K}}$) was found to be (2.0\ifmmode\pm\else\textpm\fi{}1.6)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$. From this and the known ${\mathit{P}}_{\mathit{K}\mathit{K}}$ for $^{131}\mathrm{Cs}$ we estimate a probability for zero K-shell vacancy production (shakedown) per K-shell electron capture of \ensuremath{\lesssim}2.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ for $^{139}\mathrm{Ce}$.

On the theory of electron capture from inner shells in intermediate and high-energy collisions

The impulse approximation for capture of atomic K-shell electrons by incident protons is investigated with respect to a realistic treatment of the initial and intermediate states of the atomic target. Explicit evaluations are made in the single-electron picture described by an effective target potential of Yukawa type. When compared with corresponding results within the standard hydrogenic description, it is found that the effect of proper screening is similar to the effect of off-shell factors found in the strong-potential born approximation. Effort should therefore be directed towards a study of the combined effect in order to obtain a more complete understanding of the electron capture process.

Capture of Ar K-shell electrons by protons

The total cross section for the capture of a K-shell electron from Ar by a fast proton has been measured at kinetic energies from 1.5 to 10 MeV. To ensure that the total cross section was indeed obtained the authors also measured the K-shell capture probability as a function of impact parameter at selected energies within the interval 1.5-4 MeV. The cross sections obtained are somewhat higher than previously published cross sections. The reason for the discrepancy is discussed. The new cross sections are compared with recent theoretical cross sections.