Oblique total reflection at an unmagnetized plasma

For vacuum incidence on a sharp planar, collisionless plasma interface, the transmitted normal wavenumber obeys $k_z^2=({\omega }^2/c^2)({\cos }^2\theta -{\omega }_p^2/{\omega }^2)$. Negative $k_z^2$ produces an evanescent field and total reflection in this lossless model.