You made me curious. It seems the theory is thermal, but it was never taken that seriously.

Bethe called it “absolute nonsense”—interview: https://johnhorgan.org/cross-check/oppenheimer-bethe-and-the...

Here's a student paper giving a pretty thorough analysis (AFAICT): http://large.stanford.edu/courses/2015/ph241/chung1/

Here's more discussion of it: https://history.stackexchange.com/questions/52802/where-did-...

And here (drumroll) is the original paper: https://web.archive.org/web/20200331041344/https://fas.org/s...