Emissivity of hydrogen atoms at high temperatures

A method is described for making estimates of the total emissivity of hydrogen in the temperature and pressure ranges where hydrogen atoms predominate under equilibrium conditions. For a typical geometrical depth of 50 cm, and temperatures of the order of 12 500ºK and higher, with pressures of the order of 100 atmos and higher, the emissivity approaches unity (є≳0.95), while for temperatures of the order of 9500ºK and lower, with pressures of the order of 10 atmos and lower, the emissivity approaches zero (є≾0.05). The variations of the emissivity between these approximate limits are shown graphically as functions of temperature and pressure with the geometrical depth set at 50 cm. The variation of the emissivity with geometrical depth is also shown graphically at 12 600ºK and 20 atmos