$\ensuremath{\gamma}$-ray spectroscopy of the odd-odd $N=Z+2$ deformed proton emitter ${}^{112}$Cs

$γ$ -ray spectroscopy of the odd-odd $N = Z + 2$ deformed proton emitter $^{112}$ Cs

P. T. Wady, J. F. Smith, E. S. Paul, B. Hadinia, C. J. Chiara, M. P. Carpenter, C. N. Davids, A. N. Deacon, S. J. Freeman, A. N. Grint, R. V. F. Janssens, B. P. Kay, T. Lauritsen, C. J. Lister, B. M. McGuirk, M. Petri, A. P. Robinson, D. Seweryniak, D. Steppenbeck, and S. Zhu

Phys. Rev. C 85, 034329 – Published 23 March 2012

Abstract

Gamma-ray transitions have been observed in the proton-emitting $N = Z + 2$ ( $T_{z} = 1$ ) isotope $^{112}$ Cs. The transitions have been unambiguously assigned to $^{112}$ Cs by correlation with the characteristic proton decay, using the method of recoil-decay tagging with mass selection. The measured proton-decay energy and half-life are $E_{p} = 810 (5)$ keV and $T_{1 / 2} = 470 (50)$ $μ$ s, respectively, which are consistent with previous measurements. Five $γ$ -ray transitions have been observed which appear to form a rotational sequence. The energy differences between excited states in the sequence are consistent with an assignment as the favored signature of the $ν (h_{11 / 2}) \otimes π (h_{11 / 2})$ structure. Tentative evidence for fine structure in the $^{112}$ Cs proton decay is also observed.

Received 1 December 2011

DOI:https://doi.org/10.1103/PhysRevC.85.034329

Authors & Affiliations

P. T. Wady^1,2, J. F. Smith^1,2,*, E. S. Paul³, B. Hadinia^1,2,†, C. J. Chiara^4,‡, M. P. Carpenter⁵, C. N. Davids⁵, A. N. Deacon⁶, S. J. Freeman⁶, A. N. Grint³, R. V. F. Janssens⁵, B. P. Kay^6,§, T. Lauritsen⁵, C. J. Lister⁵, B. M. McGuirk³, M. Petri^3,∥, A. P. Robinson^5,¶, D. Seweryniak⁵, D. Steppenbeck^6,**, and S. Zhu⁵

¹School of Engineering, University of the West of Scotland, Paisley PA1 2BE, United Kingdom
²Scottish Universities Physics Alliance (SUPA)
³Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE, United Kingdom
⁴Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA
⁵Physics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
⁶School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom

^*john.f.smith@uws.ac.uk
^†Present address: Department of Physics, University of Guelph, Guelph, Ontario, N1G 2W1, Canada.
^‡Present address: Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA.
^§Present address: Department of Physics, University of York, Heslington, York YO10 5DD, United Kingdom.
^∥Present address: Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
^¶Present address: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom.
^**Present address: RIKEN Nishina Center, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.

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Vol. 85, Iss. 3 — March 2012

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Figure 1
Horizontal position in the PGAC, proportional to $A / q$ , plotted against decay energy recorded in the DSSD. The data are collected into two main groups on the vertical axis: The lower group includes $A / q = 112 / 27$ and the upper group includes $A / q = 112 / 26$ . The positions of nearby $A / q$ values are marked by horizontal dashed lines. The clusters of data points corresponding to $^{109}$ I ( $A / q = 109 / 25$ ) and $^{113}$ Cs ( $A / q = 113 / 26$ ) are labeled.Reuse & Permissions
Figure 2
Panels (a) and (b) give the energies recorded in the DSSD within 1500 $μ$ s of an implanted evaporation residue. Panel (a) is the spectrum recorded from all of the data; although the mass slits are in place, decays of $^{109}$ I and $^{113}$ Cs are also present due to overlapping $A / q$ values. Panel (b) is the same spectrum but with a tighter restriction on $A / q$ (horizontal PGAC position) in order to select only $A / q = 112 / q$ residues. Panel (c) presents the time between implant in the DSSD and the decay event; the data are presented in 100- $μ$ s bins and are shifted by 70 $μ$ s to the left to account for the dead time of the data-acquisition system. The data in panel (c) are consistent with a half-life of 470(50) $μ$ s.Reuse & Permissions
Figure 3
Gamma-ray spectra recorded in this work. Panel (a) presents the projection of all $γ$ rays which are detected in coincidence with a residue at the focal plane of the FMA; the largest peaks in the spectrum belong to nuclei with $A = 112$ ( $^{112}$ I and $^{112}$ Te, as labeled). Panel (b) shows $γ$ rays correlated with proton decays of 810 keV within 1500 $μ$ s of an implant. The spectrum exhibits unknown transitions, which are assigned to the decay of excited states in $^{112}$ Cs, together with some known transitions in $^{109}$ I. Panel (c) is the same spectrum as panel (b), but with a tight condition on $A / q = 112 / q$ ; the $^{109}$ I transitions are eliminated. Panels (d) and (e) are the same as panels (b) and (c), respectively, but with the additional condition that the decay occurs more than 300 $μ$ s after the implant, in order to eliminate decays of $^{109}$ I, which has a half-life of 100 $μ$ s. The additional condition for panel (d) clearly eliminates the $^{109}$ I transitions in panel (b).Reuse & Permissions
Figure 4
The proposed level scheme of $^{112}$ Cs, deduced in this work. Transition energies are given in keV, with uncertainties of around 0.5 keV. The transitions have been ordered on the basis of intensity and by comparison to neighboring odd-odd cesium isotopes. Two transitions with energies 155 keV and, tentatively, 818 keV have been assigned to $^{112}$ Cs but are not placed in this level scheme.Reuse & Permissions
Figure 5
Calculated quadrupole-deformation parameters $β_{2}$ and excitation-energy systematics of excited states for odd-odd cesium isotopes with $110 \leq A \leq 126$ ( $55 \leq N \leq 71$ ). Panel (a) presents values of $β_{2}$ from the macroscopic-microscopic calculations of Möller, Nix, Myers, and Swiatecki (MNMS) [2], from TRS calculations [34, 35], and from HFB self-consistent mean-field calculations [36]. Panels (b) and (c) show energies of excited states in $^{112}$ Cs in comparison to the $α = 0$ [even spins, panel (b)] and $α = 1$ [odd spins, panel (c)] sequences of $ν (h_{11 / 2}) \otimes π (h_{11 / 2})$ bands in $^{114 - 126}$ Cs. The energies are shown relative to the 10 $^{+}$ [panel (b)] or 11 $^{+}$ [panel (c)] state in each nucleus. The data for $^{112, 114}$ Cs are the same in both panels; for these nuclei, only one $E 2$ sequence has been observed, which has been assumed [22] to have odd spins. The data for $^{114 - 126}$ Cs are taken from Refs. [3, 17, 21, 22, 37, 38, 39, 40, 41] with spin assignments from Ref. [42].Reuse & Permissions
Figure 6
Aligned angular momenta of the $ν (h_{11 / 2}) \otimes π (h_{11 / 2})$ odd-spin ( $α = 1$ ) bands in $^{112, 114, 116, 118, 120}$ Cs. The data for $^{114, 116, 118, 120}$ Cs are taken from Refs. [3, 17, 21, 22]. For all data points, a reference configuration with the Harris parameters [46] $J_{0} = 17.0$ MeV $^{- 1}$ $ℏ^{2}$ and $J_{1} = 25.8$ MeV $^{- 3}$ $ℏ^{4}$ [47] has been subtracted. A value of $K = 3$ has been assumed for all of the bands. The initial value of the aligned angular momentum ( $\sim$ 8 $ℏ$ ) and the CSM-predicted $ν {(h_{11 / 2})}^{2}$ (EF) and $π {(h_{11 / 2})}^{2}$ (ef) alignment frequencies for $^{112}$ Cs are marked.Reuse & Permissions

Physical Review C

covering nuclear physics

$γ$ -ray spectroscopy of the odd-odd $N = Z + 2$ deformed proton emitter $^{112}$ Cs

P. T. Wady, J. F. Smith, E. S. Paul, B. Hadinia, C. J. Chiara, M. P. Carpenter, C. N. Davids, A. N. Deacon, S. J. Freeman, A. N. Grint, R. V. F. Janssens, B. P. Kay, T. Lauritsen, C. J. Lister, B. M. McGuirk, M. Petri, A. P. Robinson, D. Seweryniak, D. Steppenbeck, and S. Zhu

Phys. Rev. C 85, 034329 – Published 23 March 2012

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Physical Review C

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γ-ray spectroscopy of the odd-odd N=Z+2 deformed proton emitter 112Cs

P. T. Wady, J. F. Smith, E. S. Paul, B. Hadinia, C. J. Chiara, M. P. Carpenter, C. N. Davids, A. N. Deacon, S. J. Freeman, A. N. Grint, R. V. F. Janssens, B. P. Kay, T. Lauritsen, C. J. Lister, B. M. McGuirk, M. Petri, A. P. Robinson, D. Seweryniak, D. Steppenbeck, and S. Zhu

Phys. Rev. C 85, 034329 – Published 23 March 2012

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$γ$ -ray spectroscopy of the odd-odd $N = Z + 2$ deformed proton emitter $^{112}$ Cs