Equilibrium properties of hydrogen gas from 5000° to 20000°K

Abstract

Equilibrium properties of hydrogen gas are calculated from 5000° to 20 000°K by considering it as a monatomic gas with imperfections. The usual "H₂ and H equilibrium" method is not suitable at high temperatures even with anharmonicity corrections. Properties are obtained from the second virial coefficient B(T) of the monatomic gas and its derivatives. For the ¹Σ state the Rydberg potential and for the ³Σ the best numerical potential is used. Ionization, higher excited states, and quantum effects are examined. The third virial coefficient for H₃ is estimated and it is shown that properties from B(T) part alone are sufficient up to pressures of 1000 atm at 10 000°K and 13 000 atm at 20 000°K. Results are compared with those of the "equilibrium constant" approach.