Hi, my studies of quantum mechanics aren't too deep (I'm still in highschool), but out of pure curiosity, I would like to see the mathematical derivations for the theoretical values for the decay rate /half-life of positronium (either for orthopositronium or parapositronium if they are different, whichever doesn't matter) as opposed to a regular hydrogen atom. I'd imagine this would involve Schrödinger's Equation and the wavefunction but not exactly sure. I'm only familiar with calculus (I-III) and some complex analysis but I can have some idea of what's going on. I tried googling for a while but that didn't work. Any links to any introductory quantum mechanics ebooks would also be extremely appreciated.