29 June 2015
Scientists have developed a mercury-based optical lattice clock and measured the mercury clock frequency using the same group’s recently developed strontium-based optical lattice clock as a reference. The research group achieved a fractional frequency uncertainty, which is smaller than the realization of the current international standard definition of the second.
http://feeds.sciencedaily.com/~r/sciencedaily/~3/wA9TB50RjpY/150629075802.htm
