High-resolution conversion electron spectroscopy of the $^{125}\mathrm{I}$ electron-capture decay

High-resolution conversion electron spectroscopy of the ${}^{125}I$ electron-capture decay

B. P. E. Tee, A. E. Stuchbery, M. Vos, J. T. H. Dowie, B. Q. Lee, M. Alotiby, I. Greguric, and T. Kibédi

Phys. Rev. C 100, 034313 – Published 16 September 2019

Abstract

The conversion electrons from the decay of the 35.5-keV excited state of ${}^{125}{Te}$ following the electron capture decay of ${}^{125}I$ have been investigated at high resolution using an electrostatic spectrometer. The penetration parameter $λ = - 1.2 (6)$ and mixing ratio $| δ (E 2 / M 1) | = 0.015 (2)$ were deduced by fitting to literature values and present data. The shake probability of the conversion electrons is estimated to be 0.5, more than two times larger than the predicted value of 0.2.

Received 17 June 2019

DOI:https://doi.org/10.1103/PhysRevC.100.034313

Physics Subject Headings (PhySH)

Electron & muon capture Nuclear structure & decays

90 ≤ A ≤ 149

Spectrometers & spectroscopic techniques

Nuclear Physics

Authors & Affiliations

B. P. E. Tee¹, A. E. Stuchbery¹, M. Vos², J. T. H. Dowie¹, B. Q. Lee¹, M. Alotiby^2,3, I. Greguric⁴, and T. Kibédi ^1,*

¹Department of Nuclear Physics, Research School of Physics, The Australian National University, Canberra, ACT, Australia
²Department of Electronic Materials Engineering, Research School of Physics, The Australian National University, Canberra, ACT, Australia
³King Abdulaziz City for Science and Technology, Riyadh, Saudi Arabia
⁴Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia

^*tibor.kibedi@anu.edu.au

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Vol. 100, Iss. 3 — September 2019

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Figure 1
The decay scheme of ${}^{125}I$ .
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Figure 2
Top: Layout of the electrostatic spectrometer [13, 14]. The details are described in the main text. Bottom: SIMION simulations for the electrostatic spectrometer. Electrons emitted from a 4 mm diameter source (A) are restricted from entering the lens stack by a 0.5 mm wide slit (B). After the main deceleration stage (C) the electrons are focused by a set of electrostatic lenses (D) on the exit plane (E) that coincides with the entrance of the hemispherical analyzer. The vertical scale is expanded by a factor of 4 for clarity, and the red lines are equipotential planes plotted at 1000 V intervals.
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Figure 3
(a) The $L_{1}, L_{2}$ , and $L_{3}$ conversion lines spectrum taken at 6.6 eV instrumental resolution, with natural widths of 2.2 eV, 2.84 eV, and 2.62 eV, respectively, as adopted from Campbell et al. [16]. The fitted curve and the background are shown in red and blue dashed curves, respectively. Note that the $L_{2}$ and $L_{3}$ lines are on a different scale to the $L_{1}$ line. The reduced $χ^{2}$ of the this fit is 1.9. The $L_{1}$ peak measured at high resolution of 4.8 eV is shown in the insert to illustrate the fitting procedure. (b) Comparison of the $L_{1}, L_{2}$ , and $L_{3}$ conversion electrons of present measurements (low-resolution mode) with those taken using magnetic spectrometers by Miura et al. [17], Brabec et al. [18], and Casey et al. [19]. All previous data were digitized and scaled to match the $L_{1}$ peak height of the present data.
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Figure 4
Spectra from three separate measurements in low-resolution mode: (a) $L_{1}$ conversion line measured together with $M_{1}$ and $M_{2}$ . A 3 keV region between the peaks is omitted. (b) $M_{1}, M_{2}$ and $M_{3}$ conversion lines. (c) $M_{1}, M_{2}$ , and $N_{1}$ conversion lines. The adopted natural widths of 10.2 eV, 3.2 eV, 3.9 eV, and 2.4 eV for the $M_{1}, M_{2}, M_{3}$ , and $N_{1}$ lines were taken from Campbell et al. [16].
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Figure 5
Ratios of the experimental conversion coefficients to the calculated values using current evaluated nuclear parameters, $λ = - 1.2 (6), δ = 0.015 (2)$ (black dots), and evaluated nuclear parameters by Brabec et al. [18] in 1982 (blue stars, shown without uncertainties for clarity). White circles represent experimental values that are not included in the least-square fitting for the evaluation of current adopted nuclear parameters. The left panel shows the nuclear science reference key numbers (see references in Table 3) and the corresponding measured quantities. The data from 1959Na06 [44] (uncertainties are not quoted in that paper) is included in this figure for comparison. Note the ratios for $δ$ are not plotted due to their large variations and errors.
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Physical Review C

covering nuclear physics

High-resolution conversion electron spectroscopy of the ${}^{125}I$ electron-capture decay

B. P. E. Tee, A. E. Stuchbery, M. Vos, J. T. H. Dowie, B. Q. Lee, M. Alotiby, I. Greguric, and T. Kibédi

Phys. Rev. C 100, 034313 – Published 16 September 2019

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Physical Review C

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High-resolution conversion electron spectroscopy of the I125 electron-capture decay

B. P. E. Tee, A. E. Stuchbery, M. Vos, J. T. H. Dowie, B. Q. Lee, M. Alotiby, I. Greguric, and T. Kibédi

Phys. Rev. C 100, 034313 – Published 16 September 2019

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High-resolution conversion electron spectroscopy of the ${}^{125}I$ electron-capture decay