I'm pretty sure раз means in between
Here раз- means "up" or "out" I guess. I'd appreciate if you suggest a word that better of all reflects the concept:
Here's the situation:
Somebody is being interrogated by a detective but the suspect refuses to reveal anything he has in his mind. He's "locked" and needs "unlocking".
So the detective resorts to various tricks and things to "разговорить" the suspect so that he would let out his secrets.
So basically "разговорить" means "to make somebody more talkative".

P.S. I guess impulse meant "говорить" vs "разговаривать", not sure tho. Разговорить is too proficient a word for a learner.