of oxygen molecules under these conditions is 3.58 x 1018
molecules m-2 s-1
The flux is directly proportional to the pressure : consequently a decrease in pressure by 6 orders of magnitude (all other conditions remaining the same) leads to a corresponding decrease in the flux i.e.
F = 3.58x1024 x ( 10-6 / 1 )
⇒ F = 3.58 x 1018 molecules m-2 s-1