A search was made with a sea water sample taken at a depth of 4000 m for anomalously heavy hydrogen dating from the early Universe. A technique of accelerator mass spectrometry involving a time-offlight spectrometer was used. A new upper limit for the concentration of heavy particles in hydrogen is set around 4 X lo-'' in the mass range of 5-1600 u at a 95% confidence level.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.