Most Helpful Guy
It sounds like he is head over heels. Especially our agegroup. We don't act like that towards girls we are not interested in, especially in a professional environment.
You could safely ask him out, I think, without really worrying about rejection. If he says he is busy, he probably really is, so have a few time slots to choose from.
I might also warn about the dangers of in-office relationships. I am sure you know all about that. But I'm just answering the question here :)