This function calculates the free-air diffusion coefficients
of different gases for a given temperature and pressure.
Arguments
- gas
(character) One of "CO2","CH4","N2O","O2","N2"
- t
(numeric) temperature in °C
- p
(numeric) pressure in hpa
References
Massman, W. J. A review of the molecular diffusivities of H2O,
CO2, CH4, CO, O3, SO2, NH3, N2O, NO, and NO2 in air, O2 and N2 near STP.
Atmospheric Environment 1998, 32(6), 1111–1127
