http://en.wikipedia.org/wiki/Julius_and_Ethel_Rosenberg

Ethel Greenglass Rosenberg (September 28, 1915 – June 19, 1953) and Julius Rosenberg (May 12, 1918 – June 19, 1953) were American communists who were executed in 1953 for conspiracy to commit espionage. The charges related to passing information about the atomic bomb to the Soviet Union. This was the first execution of civilians for espionage in United States history.

http://www.guardian.co.uk/world/2010/sep/18/fbi-sting-venezuela

An American nuclear scientist and his wife were arrested yesterday, accused of conspiring to sell atomic secrets to Venezuela after allegedly being caught in an FBI sting by an agent posing as a representative of the Venezuelan government.