calculating single molecules collision time

[karadril]

Hi

I have a question regarding the diffusion rates and the time it takes 2 single molecules to react with eachother.

If you don't know the answer yourself but you might have a good idea on where to find the correct information, that would be greatly appreciated as well.

So the problem is this: I have 2 molecules (of different sizes), contained in a small cube (lets say 1µm3). I want to know how long it would take on average for them to react with each other (by random diffusion).

Probably this problem needs to be simplified to "how long it would take for them to collide with eachother" (I don't know how likely a reaction between two colliding molecules is, probably depends on a whole bunch of parameters).

The Einstein diffusion laws don't seem to be sufficient for me in their standard form.

Many thanks to anyone who can help me