Limit on majoron emission in beta beta decay of 100Mo.

We report the results of an experimental search for double-$\ensuremath{\beta}$ decay of $^{100}\mathrm{Mo}$. No evidence is found for the decay mode with majoron emission, yielding a half-life limit of 3.3\ifmmode\times\else\texttimes\fi{}${10}^{20}$ yr with 90% confidence. We also obtain a lower limit for the two-neutrino mode of 3.8\ifmmode\times\else\texttimes\fi{}${10}^{18}$ yr.