Cluster virial expansion of the equation of state for hydrogen plasma with e-H2 contributions

© 2015 American Physical Society. The equation of state of partially ionized hydrogen plasma is considered with special focus on the contribution of the e-H2 interaction. Traditional semiempirical concepts such as the excluded volume are improved using microscopic approaches to treat the e-H2 problem. Within a cluster virial expansion, the Beth-Uhlenbeck formula is applied to infer the contribution of bound and scattering states to the temperature-dependent second virial coefficient. The scattering states are calculated using the phase expansion method for the polarization interaction that incorporates experimental data for the e-H2 scattering cross section. We present results for the scattering phase shifts, differential scattering cross sections, and the second virial coefficient due to the e-H2 interaction. The influence of this interaction on the composition of the partially ionized hydrogen plasma is confined to the parameter range where both the H2 and the free-electron components are abundant.