$\ensuremath{\alpha}$ decay of the $\ensuremath{\pi}{h}_{11/2}$ isomer in $^{164}\mathrm{Ir}$

$α$ decay of the $π h_{11 / 2}$ isomer in ${}^{164}{Ir}$

M. C. Drummond et al.

Phys. Rev. C 89, 064309 – Published 16 June 2014

Abstract

The $α$ -decay branch of the $π h_{11 / 2}$ isomer in ${}^{164}{Ir}$ has been identified using the GREAT spectrometer. The ${}^{164}{Ir}$ nuclei were produced using the $^{92} Mo (^{78} Kr, p 5 n)^{164} Ir$ reaction and separated in flight using the recoil ion transport unit (RITU) gas-filled separator. The measured $α$ -decay energy of $6880 \pm 10$ keV allowed the excitation of the $π h_{11 / 2}$ state in ${}^{160}{Re}$ to be deduced as $166 \pm 14$ keV. The half-life of ${}^{164}{Ir}$ was measured with improved precision to be $70 \pm 10 μ$ s and an $α$ -decay branching ratio of $4 \pm 2$ % was determined. Improved half-life and branching ratio measurements were also obtained for ${}^{165}{Ir}$ , but no evidence was found for the ground-state decays of either ${}^{164}{Ir}$ or ${}^{165}{Ir}$ .

Received 15 April 2014

DOI:https://doi.org/10.1103/PhysRevC.89.064309

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Vol. 89, Iss. 6 — June 2014

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Figure 1
Schematic diagram showing the expected proton and $α$ decays of states in ${}^{164}{Ir}$ . The odd neutrons in ${}^{156}{Ta}$ , ${}^{160}{Re}$ , and ${}^{164}{Ir}$ are proposed to occupy $ν f_{7 / 2}$ orbitals [4, 5]. The discovery of the $α$ decay of the $π h_{11 / 2}$ isomer in ${}^{164}{Ir}$ shown by the dotted line is presented in this work, but no evidence could be found for the proton decay of the $π d_{3 / 2}$ ground state indicated by the dashed line.
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Figure 2
(a) Energy spectrum of decay events occurring within 0.5 ms of an ion being implanted into the same DSSD pixel. (b) Energy spectrum of these events that are followed within 28 ms by an $α$ decay of ${}^{163}{Os}$ . (c) Energy spectrum of decay events that occur within 0.35 ms of an ion implantation and are followed within 3 ms by a daughter energy characteristic of ${}^{160}{Re}$ ground-state proton decays. Escaping $α$ particles detected in the array of PIN diodes are not included in these spectra.
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Figure 3
(a) A section of a parent-daughter decay correlation matrix showing the correlations between proton decays of ${}^{160}{Re}$ and ${}^{165}{Ir}$ with the $α$ decays of their respective daughters, ${}^{159}W$ and ${}^{164}{Os}$ . The maximum time intervals between the implantation and parent decay and between the parent and daughter decays were 1 ms and 63 ms, respectively. (b) A section of the same decay correlation matrix featuring the $α$ decays of ${}^{165}{Ir}$ correlated with those of its daughter ${}^{161}{Re}$ . Correlations of ${}^{163}{Os}$ - ${}^{159}W$ , ${}^{161}{Re}$ - ${}^{157}{Ta}$ , and ${}^{162}{Re}$ - ${}^{158}{Ta}$ are also visible. Panels (c) and (d) are projections of panels (a) and (b) showing the energies of the parent decays.
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Figure 4
$Q$ values of $α$ decays of $π h_{11 / 2}$ states in odd- $Z$ nuclei and the ground states of even- $Z$ nuclei. The measured value for ${}^{164}{Ir}$ obtained in the present work and the $Q$ value for ${}^{160}{Re}$ deduced from it are indicated by the larger red symbols. Data are taken from Refs. [3, 4, 16, 17, 18, 19, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40]. The value plotted for ${}^{164}{Re}$ $_{89}$ corresponds to the $α$ -particle energy of 5486 keV discussed in Ref. [39].
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Figure 5
Reduced proton-decay widths of $π h_{11 / 2}$ states of Ta, Re, Ir, and Au nuclei. (a) Values calculated using the WKB approximation compared with spectroscopic factors from low-seniority shell-model calculations (dashed lines) and BCS theory (dotted lines). (b) Values calculated using the simple formula from Ref. [45]. Experimental data are taken from Refs. [2, 3, 4, 5, 16, 19, 23, 38, 46], and the present work.
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Physical Review C

covering nuclear physics

$α$ decay of the $π h_{11 / 2}$ isomer in ${}^{164}{Ir}$

M. C. Drummond et al.

Phys. Rev. C 89, 064309 – Published 16 June 2014

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Physical Review C

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α decay of the πh11/2 isomer in Ir164

M. C. Drummond et al.

Phys. Rev. C 89, 064309 – Published 16 June 2014

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$α$ decay of the $π h_{11 / 2}$ isomer in ${}^{164}{Ir}$