The collision diameter (kinetic theory) can be estimated from the thermophysical parameters as follows:
[σ]2 = (2/3)(M.R.T)0.5/(N[π]1.5[η])
M= 86.18
R = 8.314[×]107
T = 353
[π] = 3.14
N = 6.02[×]1023
[η] = 7.85[×]10-5 taken from NIST
I got for the estimated collision diameter [σ] = 6.37 [×]10-8 cm = 0.637 nm.
Of course, the collision diameter can be estimated by other methods. I don't know the accepted error % in all the estimates.