We study binary collisions of metastable calcium atoms (${}^{40}$Ca) in an optical dipole trap. Collisions between ${}^3{P}_0$ atoms and between ${}^3{P}_0$ and ${}^1{S}_0$ atoms are considered. In the former case, the elastic and inelastic collision parameters are found to be $5.4\times {10}^{-11}$ and $3.6\times {10}^{-11}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$, respectively. A fraction of the collisions between ${}^3{P}_0$ atoms is found to produce cold trapped atoms in the singlet ${}^1{S}_0$ state, suggesting that the internal energy for these collisions is dissipated by radiation. For collisions between ${}^3{P}_0$ and ${}^1{S}_0$ atoms, we find a two-body loss parameter of $8.5\times {10}^{-11}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$. Our observations show that metastable calcium samples in the ${}^3{P}_0$ state are not stable at high densities, which limits their usefulness in quantum computing or many-body quantum simulation schemes.

• Received 18 November 2013

DOI:https://doi.org/10.1103/PhysRevA.88.063639