The idea for this question comes from Jan's comment over here. I realized I don't know how I would compute the probability of tunneling in the process of a reaction.
When I say "compute" I don't mean something rather trivial like finding the probability of a quantum harmonic oscillator being past the classical turning points which can just be done analytically.
For instance, if I were studying some reaction computationally (to estimate rate constants or something which depends on tunneling) and constructed a potential energy surface for a bond-breaking process, let's say the transfer of a hydrogen, how do I account for the possibility of tunneling through the barrier along this reaction coordinate?
I could speculate, but I imagine I would be wrong. How would one do this using common computational software and techniques?