Test of the Symmetrization Postulate for Spin-0 Particles

We investigated the spectrum of the ${}^{16}{\mathrm{O}}_2$ molecule by high-sensitivity laser spectroscopy and searched for transitions involving states which are antisymmetric under the exchange of the nuclei. These states are forbidden by the symmetrization postulate of quantum mechanics. This is the first reported experiment to test the symmetrization postulate for integer-spin particles to high precision. Our data set an upper limit of $5\times {10}^{-7\mathrm{}}$ to a possible violation of this postulate.