K-shell ionization in alpha-decay of polonium isotopes

Eremin, N.V.; Strizhov, V. F.; Tulinov, A.F.; Uljanova, O. V.

doi:10.1007/bf02735180

Cited by 11 publications

(7 citation statements)

References 4 publications

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“…The cited scattering calculations reproduce a large volume of both light and heavy-ion scattering data [9]. The half trajectory calculations agree with both 4oAr induced fusion reactions at 4.5 MeV/A [10] and measurements of K-vacancy production in a decay [8,11] to better than a factor of two. Considering the above, we will use an estimate of P~-0.7%; to which we estimate an uncertainty of a factor of two.…”

supporting

confidence: 60%

Estimation of the time scale of last chance alpha emission using an ‘‘atomic clock’’

et al. 1994

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The probability of Slling a K-vacancy, created on the incoming part of the coQision, before nparticle emission is used to time the decay of Yb compound nuclei. These nuclei were produced in the fusion reaction 250 MeV Ni + Mo. In general the nuclear decays are too fast to be timed by this clock, however, n-particle emitting compound nucleus states have lifetimes sufBciently long for this technique to work when both the a-particle has low energy and the compound nucleus spin is large. This supports the existence of last, or near last, chance o;-particle emission in the deexcitation of high spin compound nuclei.PACS number(s): 24.60. Dr, 25.70.Gh Thirty years ago Gugelot [1] pointed out that one can calibrate the decay width (I', ) of a compound nucleus in terms of the K x-ray width (I' ) for atomic vacancies. All one has to do is prepare an atoxn with an excited nucleus and a K vacancy and then measure the branching ratio I' /I', . In practice, there are several problems in applying this idea. The K-vacancy production probabilities P~are low (of the order of 1%) for typical low energy fusion reactions and, in contrast to atomic collisions below the Coulomb barrier, the x rays of interest must be detected in a large background resulting &om internal conversion x rays and p rays emitted by excited nuclear reaction products. Another important issue is photon production from the filling of vacancies in a charged particle exit channel during the time after exnission but before the emitted particle is well outside the K-shell Bohr radius (molecular orbital emission). Due to these problems, this old idea has met with success only recently [2][3][4].This technique is best suited to the study of the lifetimes of last or near last chance decays of compound systems in the bottom portion (high charge) of the periodic table. Only under these conditions does the K-vacancy lifetime approach the compound nuclear lifetime. Two interesting topics for which this technique is quite promising are: (1) the study of slow fission components and (2) slow "yrast" a-particle emission. The former involves actinide nuclei for which the K-vacancy lifetime is less than 10~s, and the latter, heavy rare earth nuclei with Kvacancy lifetixnes between 10 and 10 s. The recent paper by Molitoris et al. [4] addresses the first of these topics and this work deals with the second.Statistical model codes predict that the emission of a particles competes with p-ray emission at very low excitation energies when the nuclei are trapped near the yrast line at high to moderate spins [5,6]. Grover and Gilat first discussed this process in work published 25 years ago [5]. These early calculations, as well as more recent ones [7], predict that these "stretched" and "last chance" o. particles would be emitted &om states with lifetimes similar to the K-vacancy lifetime and therefore present an ideal application of the atoxnic clock xnethod. The predicted a-particle energies are low for these "last chance" particle emissions which, despite the angular moxnentum re...

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supporting

confidence: 60%

Estimation of the time scale of last chance alpha emission using an ‘‘atomic clock’’

et al. 1994

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“…Thorium was chosen in order to examine the dependence of the alignment on the charge of the alpha particle emitter. In order to obtain the cross sections (14) necessary to calculate alignment (15), a particular representation of the electronic wavefunctions and model of the alpha particle motion must be selected. For the wavefunctions, we make use of single particle Dirac wavefunctions generated using a screened potential [17] to account for the dominant part of the electron-electron interaction effects.…”

Section: Resultsmentioning

confidence: 99%

“…We have chosen to calculate alignment (15) for polonium and thorium atoms, specifically for their isotopes 210 Po and 228 Th. The choice of 210 Po has been made as an extensive body of experimental and theoretical research exists on this element [9,[23][24][25][26]. 228 Th was chosen in order to examine the dependence of the alignment on the charge of the alpha particle emitter.…”

Section: Resultsmentioning

confidence: 99%

“…To understand this process, a full theoretical treatment has been given in section 2 that accounts for shake-off and recoil effects, screened relativistic wavefunctions and the real motion of the alpha particle. We have applied this theory by way of equation (14) to determine alignment values (15) for the process of emission of an electron from 2p 3/2 shell of Polonium and Thorium atoms. These results have been compared to those presented in [5].…”

Section: Discussionmentioning

confidence: 99%

“…With the help of equations (14) and (15) we can calculate the relativistic forms for the cross sections and alignment of alpha decay induced atomic ionisation. In the following section, we proceed to show our results for the calculation of A 20 for the ionisation process whereby an electron is ejected out of the 2p 3/2 bound state of Polonium and Thorium nuclei.…”

Section: Cross Sections and Alignmentmentioning

confidence: 99%

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Alignment of atomic inner-shells following alpha-decay-induced ionization

McConnell¹,

Artemyev²,

Surzhykov³

2011

J. Phys. B: At. Mol. Opt. Phys.

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Nuclear alpha decay may induce the emission of electrons originally bound to the nucleus. If the ejected electron initially resides in a state with j > 1/2, the residual ion may be aligned. In this article, such an alignment is examined for the L III ionisation of heavy atoms. This work pays particular attention to the effects of shake-off, recoil and nuclear potential screening. To illustrate these effects, we have performed calculations for the decay of the nuclei of neutral Polonium and Thorium atoms over a range of commonly encountered alpha particle kinetic energies (α ∼ O(10 MeV)).

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