On the pure dipole shift for hydrogen lines in a plasma

Abstract

In the light of recent discussion on the shift of hydrogen lines in dense plasmas we give an analytic proof that within the standard assumptions of no quenching, no fine structure and density matrix factorization the dipole shift is identically zero, regardless of the details of the interaction, as long as it is dipole. This refutes some theoretical explanations that match observed shifts by invoking various effects based on a dipole interaction.