Angular correlation measurements have been performed on 12 direct and 4 skip cascades in $^{142}\mathrm{Ce}$, all involving the 641-keV ${2}^{+}$ \ensuremath{\rightarrow} ${0}^{+}$ transition. The $^{142}\mathrm{Ce}$ levels were populated in the ${\ensuremath{\beta}}^{\ensuremath{-}}$ decay of fission-product $^{142}\mathrm{La}$ produced as a decay product of $^{142}\mathrm{Xe}$ at the TRISTAN on-line isotope-separator facility. Spin-parity assignments or preferences have been made for all 13 excited levels below 3 MeV previously known to be populated in this decay. In addition, a new ${0}^{+}$ level is established at 2030 keV in $^{142}\mathrm{Ce}$. These levels are described in terms of vibrations of a spherical nucleus. An alternate interpretation in terms of quasirotational bands is also presented.RADIOACTIVITY $^{142}\mathrm{La}$(from $^{142}\mathrm{Xe}$ decay); measured $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}(\ensuremath{\theta})$. $^{142}\mathrm{Ce}$ deduced $J$, $\ensuremath{\pi}$. Mass-separated $^{142}\mathrm{La}$ activity.

A seven-detector γ-γ angular-correlation apparatus has been constructed to study short-lived fission product nuclei produced by the TRISTAN on-line isotope separator system. The apparatus employs either seven NaI(Tl) detectors or six NaI(Tl) detectors and one Ge(Li) detector. A 16 384-channel analyzer may be used in conjunction with a series of single-channel discriminators to measure correlations simultaneously on all cascades involving a single γ-ray transition. Alternatively, a buffer tape system may be used to record data simultaneously on all cascades in a decay scheme. The apparatus has been tested on cascades in 138Ba from the decay of 138Cs. The results for three direct and two skip cascades are consistent with the known spins of 2+, 4+, 4+, and 3+ for the levels at 1436, 1899, 2308, and 2446 keV in 138Ba, respectively. In addition mixing ratios of 0.01±0.03, 0.05−0.12+0.20, and 0.10±0.03 have been obtained for the transitions at 1009, 409, and 547 keV in this nucleus.