Estimated values for alpha CO 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)
61.50   3.73e-02
59.00   1.88e-02
56.50   8.87e-03
54.00   3.90e-03
51.50   1.58e-03
49.00   5.79e-04
46.50   1.90e-04
44.00   5.49e-05
41.50   1.36e-05
39.00   2.80e-06
36.50   4.63e-07
34.00   5.87e-08
31.50   5.36e-09
29.00   3.24e-10
26.50   1.16e-11
24.00   2.11e-13
21.50   1.54e-15
19.00   3.14e-18
16.50   1.01e-21
14.00   1.97e-26
