I know the usage of 一下子 but I don't really understand about 一刹那 and 一时
一下子 = all of a sudden. e.g. 一下子不見了 gone all of a sudden
刹那 is a Buddhism term for a time unit. In one flick of a finger, 60 刹那 would pass
一刹那 = a very brief moment. e.g. 在一刹那間 (in the blink of an eye) = almost instantly
一时 = at the moment/ at the time. e.g. 一时找不到人选 (Can't find a candidate at the moment/ at the time)
一瞬間 (in the time of one glance), 一息間 (in the time of one breath) and 瞬息間 are the terms similar to 刹那間 (in the time of a 刹那). They can all be translated as "in the blink of an eye"