Static and dynamic shifts of spectral lines

The relationship between static and dynamic contributions to line shifts in hydrogen plasmas is investigated with use of a set of approximations common to line-shape theories. It is shown that when the coupling between states of different principal quantum number is neglected, the asymmetry of the second-order width operator (due to detailed balance with the plasma) introduces a shift whose impact limit cancels approximately one-half of the second-order static shift. While the details of the calculation depend upon the approximations made, the primary conclusion that the second-order shift due to fluctuations can be as important as that due to static correlations does not. The possible implications of this result for plasmas with charged radiators are briefly discussed.