Level structure of light even xenon nuclei populated in the decays of isomeric and ground states of 118,120,122Cs

Rich band structure and multiple long-lived isomers in the odd-odd Cs118 nucleus

“…The observation of these delayed γ -ray cascades lead to a state located 126 keV below the 7 + isomer, to which we tentatively assigned spins and parities based on the analysis of the isomer decay, as described in the following. No other transitions have been observed at the MARA focal plane in coincidence with the delayed transitions depopulating the 7 + isomer, indicating that the three γ -ray branches populate one of the two known long-lived isomers, which can only be the I = (6, 7, 8), T 1/2 = 17(3) s isomer [12], since the observed delayed transitions depopulate the high-spin 7 + state and cannot have the high multipolarity required to populate the I = 2 isomer [11]. A half-life T 1/2 = 0.55(6) μs has been extracted from the fit of the time spectrum obtained by summing the time spectra of the 79-and 126-keV depopulating transitions of the 7 + isomer, as shown in Fig.…”

“…This indicates the isomeric character of the 7 − bandhead, with a half-life of at least several microseconds. We identify the bandhead of Band 3 with the T 1/2 = 17(3) s isomer for which a spin I = (6, 7, 8) has been suggested [12], selecting thus I = 7 among the three possible spin values, and we assign it negative parity, leading therefore to I π = 7 − for the T 1/2 = 17(3) s isomer.…”

“…The lightest odd-odd Cs nucleus with known spectroscopic information is the proton emitter 112 Cs [9,10], in which five firm and two tentative transitions have been identified and assigned to the π h 11/2 ⊗ νh 11/2 configuration based on systematics [5]. The low-lying states of Cs nuclei have been studied over many years, also exploiting the high yields of radioactive beams of Cs isotopes at ISOL facilities [11,12]. Two long-lived isomers have been identified in 118 Cs, the nucleus studied in the present work, one with T 1/2 = 14(2) s and low spin I = 2, and the other with T 1/2 = 17(3) s and high spin I = (6, 7, 8) [12,13].…”

“…The low-lying states of Cs nuclei have been studied over many years, also exploiting the high yields of radioactive beams of Cs isotopes at ISOL facilities [11,12]. Two long-lived isomers have been identified in 118 Cs, the nucleus studied in the present work, one with T 1/2 = 14(2) s and low spin I = 2, and the other with T 1/2 = 17(3) s and high spin I = (6, 7, 8) [12,13]. The magnetic and spectroscopic quadrupole moments of the longlived isomers have been measured in an extended range of Cs nuclei, from 118 Cs to 145 Cs [13], which in many cases led to firm spin and parity assignments, and also to experimentally established deformation of the long-lived isomers on which rotational bands can be built.…”

Isotopically selective dissociation of COCl2molecules in the radiation field of a pulsed CO laser

“…The decays of even-mass caesium isotopes from A = 122 to 1 18 have already been studied by our group (Genevey-Rivier et al 1977) with high-purity sources at the IsOLDE separator on-line with the CERN synchrocyclotron. So far, for the odd-mass caesium decays, little is known about nuclei with A < 125.…”