"Now I am become death, the destroyer of worlds". Robert Oppenheimer is often credited with saying these words after witnessing the power of an atomic bomb, but did he actually say them? Are there any reliable sources on this?

Oppenheimer claimed to have quoted the Gita during Trinity in a 1965 interview for the documentary The Decision to Drop the Bomb- the quote is about 24 minutes into the link. More can of course be said on this matter, but you might want to check out /u/restricteddata 's blog post Oppenheimer and the Gita which draws a bit from the paper "The Gita of J. Robert Oppenheimer"-pdf warning by James Hijiya.