Let me be not the first to declare clulessness but the first to prove it. I’ll do that by a series of tactics. First, I will completely misunderstand the question. Since it’s me, you can take that for granted and assume as much without fear. Second, I will draw on memory, and since most of what I’ve already forgotten wouldn’t be recollected accurately anyway, the fact the answer was never covered up in the dark recesses of memory to begin with, that too can be set aside as wholly unhelpful. Finally, I will begin building the bridge to your answer by either giving falsehoods that others will correct or it’ll be called out as irrelevant information that can be most useful for others to contrast with the right answer.
Your question assumes a falsehood—either that or a distorted meaning divergent to what is actually put to wording. They don’t exchange. So, no frequency. There are exchanges, but the protons and neutrons are not exchanged.
It sounds to me you’re interested in the frequency of whatever pion exchanges that do occur in the nucleus where the protons and neutrons reside. 26 nanoseconds?
