Well, since this is a physics forum too, I guess this is semi-appropiate. The current definition I have of the length of a second in the frequency of one type of radiation of a Cesium-133 atom... but which radiation type would that be is what I want to know. I know I could probably search online and find out myself, but I''m already here, my connection is slow, and it''s not a pressing question. And I want to see whether or not this is common knowledge or not

IIRC, cesium-133 undergoes beta decay; that is, it releases a beta particle.

Yes, my chemistry skills are finely tuned. Thanks for the answer; you saved a lazy man some work