What sutta refers to 'emptiness in small space'?

I remember reading about one sutta "emptiness in small gap". Since consciousness (Vijñāna) raises and falls all the time, between each consciousness there is a very small and briefest gap where Vijñāna doesn't take place. If i remember correctly, Buddha might have said about this emptiness as FYI. Anyone could help me find sutta about "emptiness in small gap" or "emptiness in small space", or "void in tight space". i want to study this sutta again to see if buddha ralated this emptiness to vimutti or maha-sunyata. thanks