# I Fusion half-life of diprotium molecule

1. May 17, 2017

### snorkack

A diprotium molecule might undergo tunnelling to fuse by two reactions:
1. p+p→d+e+e
2. p+p+e→d+νe
What is the half-life for the fusion of an isolated diprotium molecule in its ground state (vibrational and rotational)?
Naturally big, but also naturally finite. And might be computed.
An estimate from Nature, in 1989:
www.fulviofrisone.com%2Fattachments%2Farticle%2F358%2FCalculated%2520fusion%2520rates%2520in%2520isotopic%2520and.pdf

The estimate seems to be in the region of 1056 years.
He says that his estimate was 10 orders of magnitude shorter than preceding ones.
While it is a theoretical field, he quotes several preceding works from 1980s.
28 years have passed since. What might be current best estimates for the half-life of diprotium molecule?

2. May 17, 2017

### Staff: Mentor

Much longer than the most conservative estimates for proton decay for every possible discussed mechanism of baryon number violating processes. If a process is so rare that it doesn't happen, theorists rarely spend time on a more precise estimate. The SM $\tau \to \mu \mu \mu$ and $\mu \to e e e$ processes are another example. You can find many estimates for their branching fraction in various BSM models, but the best SM prediction is something like "10-50, give or take several orders of magnitude".