Effects of Coulomb Collisions on the Dispersion Relation of Longitudinal Plasma Oscillations

The dispersion relation of longitudinal electron-plasma oscillation for a fully ionized plasma with equal electron and ion temperatures in the absence of an external magnetic field has been calculated by taking into account of both the electron-ion and electron-electron collisions. The calculation utilizes the absorptive parts of the collisional conductivity functions derived by DuBois and coworkers for obtaining the polarizability parts via Kramers-Kronig relation. The results are presented in graphical forms and show that the longitudinal plasma oscillations are shifted toward higher frequencies from the resonance of collisionless plasma predicted by the Bohm-Gross dispersion relation.