We report the results of an experimental search for neutrinoless double-β decay using isotopically enriched foils of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ interleaved in a stack of 40 silicon detectors. With an exposure of 69.9 mole days, we place lower half-life limits on the $J^P$${=0\mathrm{}}^{+}$→$0^{+}$ transition of 4×${10}^{21}$ yr (68% C.L.) and on the $0^{+}$→$2^{+}$ transition of 4×${10}^{20}$ yr (68% C.L.).

• Received 17 July 1989

DOI:https://doi.org/10.1103/PhysRevLett.63.1671