Estimated values for alpha N2 from:
Brown, G.N., and W.T. Ziegler 1980.  Vapor pressure and heats of vaporization and sublimation of liquids and solids of interest in cryogenics below 1-atm pressure.  Adv. Cryo. Eng. 25, 662-670.
T(K)     P(bar)
35.40   3.61e-06
32.00   2.51e-07
29.00   1.42e-08
26.00   4.11e-10
23.00   4.75e-12
20.00   1.45e-14
17.00   5.90e-18
14.00   9.03e-23
