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Article
Title	$\beta$-decay studies of $^{135-137}$Sn using selective resonance laser ionization techniques
Author(s)	Shergur, J ; Brown, B A ; Fedosseev, V ; Köster, U ; Kratz, K L ; Seweryniak, D ; Walters, W B ; Wöhr, A ; Fedorov, D ; Hannawald, M ; Hjorth-Jensen, M ; Mishin, V I ; Pfeiffer, B ; Ressler, J J ; Fynbo, H O U ; Hoff, P ; Mach, H ; Nilsson, T ; Wilhelmsen-Rolander, K ; Simon, H ; Bickley, A A
Affiliation	(CERN)
Publication	2002
In:	Phys. Rev. C 65 (2002) 034313/1-9
DOI	10.1103/PhysRevC.65.034313
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE ; IS393
Abstract	The decays of the very neutron rich Sn isotopes $^{135-137}$Sn were studied at CERN/ISOLDE using isotopic and isobaric selectivity achieved by the use of a resonance ionization laser ion source and mass spectroscopy, respectively. Neutron decay rates, $\gamma$-ray singles, and $\gamma\gamma$-coincidence data were collected as a function of time. The half-life ( T$\scriptstyle_{1/2}$ ) and delayed neutron emission probability ( $p_{n}$ ) values of $^{135}$Sn were measured to be 530(20) ms and 21(3)%, respectively. For $^{136}$Sn, a T$\scriptstyle_{1 /2}$ of 250(30) ms was determined along with a $p_{n}\,$ value of 30(5) %. For $\,^{137}$Sn, a T$\scriptstyle_{1/2}$ of 190(60) ms and a $p_{n}$ value of 58(15)% were deduced. Identification of low-energy transitions in $^{135}$Sb was made possible by comparison of laser-on and laser-off $\gamma$-ray spectra. Those data combined with $\gamma\gamma$-coincidence spectra were used to construct a level scheme for $^{135}$Sb that includes an unexpectedly low first excited state at 282 keV. A ground state $\beta$-branch of 33.2% was measured by following the growth and decay of the $^{135}$Sb daughter. Shell-model calculations are consistent with the observed $^{135}$Sb level structure and can account for a lowered first excited state.

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