[en] New limits on half-lives for several double beta decay modes of ¹⁰⁰Mo were obtained with a novel experimental system which included thin source films interleaved with a coaxial array of windowless silicon detectors. Segmentation and timing information allowed backgrounds originating in the films to be studied in some detail. Dummy films containing ⁹⁶Mo were used to assess remaining backgrounds. With 0.1 mole years of ¹⁰⁰Mo data collected, the lower half-life limits at 90% confidence were 2.7 /times/ 10¹⁸ years for decay via the two-neutrino mode, 5.2 /times/10¹⁹ years for decay with the emission of a Majoron, and 1.6 /times/ 10²⁰ years and 2.2 /times/ 10²¹ years for neutrinoless 0⁺ → 2⁺ and 0⁺ → 0⁺ transitions, respectively. 50 refs., 38 figs., 11 tabs