As stated before, we assumed that d was approximately equal to the mean free path of H 2 O molecule in the air. The mean free path was estimated to be 201 nm for the height of 850 m above sea level and the air temperature T 1 , 284.240 K. Then we obtained T = (284.243 -1.1 × 10 -4 ) K. Now that we have estimates for T and T L , we can limit the ranges of E 1 and E 2 by using Eqs (31) and (32),