Search for superheavy hydrogen in sea water

We report the results of an experiment designed to search for superheavy isotopes of hydrogen. Based on the centrifugation of sea water, followed by atomic spectroscopy, it is sensitive to large masses from ${10}^4$ up to ${10}^8$ GeV/${\mathit{c}}^2$. The relative abundance of such hypothetical atoms, compared to ordinary hydrogen, is found to be less than about 6×${10}^{\mathrm{-}15}$. This may be used to exclude charged dark matter particles between ${10}^4$ and ${10}^7$ GeV/${\mathit{c}}^2$.