Thermodynamics and transport properties of high-density hydrogen plasma

The development of new technologies and experimental techniques has triggered intensive theoretical research on the modeling of spatially confined quantum systems and also of extreme-high-pressure plasmas like in stellar envelopes. The thermodynamic properties and transport coefficients of non-ideal, high-density hydrogen plasma have been investigated, accounting for quantum effects due to the change in the energy spectrum of atomic hydrogen when the electron-proton interaction is considered embedded in the surrounding particles. High-density conditions have been simulated assuming atomic hydrogen subject to a screened Coulomb potential, to account for the surrounding plasma. The ionization equilibrium is affected by the pressure ionization phenomenon, deeply investigated in literature as resulting from the non-ideal Debye-Hückel corrections. The influence of the plasma leads to a correction term lowering the ionization potential, that corresponds to the so-called self-energy shift, Δ = −e²/λ_D , thus leading to an effective value Ieff = I₀−Δ, where I₀ is the ionization potential of the isolated, unperturbed hydrogen atom. Actually an additional lowering is due to the effect of the presence of a screened Debye potential on the eigenvalues for electronic levels obtained solving the Schrödinger equation, correspondingly observed in the case of box confinement. Furthermore the ensemble of levels affects also the internal partition function of H atom in the Saha equation. The effects of non-ideality in the thermodynamics of high-density hydrogen plasma on transport properties have been investigated in the frame of the Chapman-Enskog theory.The electrical conductivity of Debye plasma also exhibits a dependence on the total electron density that is affected by the pressure ionization, i.e. the minimum behavior of the conductivity and the Mott transition merging to the fully ionized regime. (author)