Upper-lower state interference term in Stark-broadening theory: Comment on a paper by J. D. Hey and H. R. Griem

Objections are presented to a recent explanation by Hey and Griem of the discrepancy between measured and calculated values for the center of $H_{\alpha }$. Their suggestion that the upper-lower state interference term occurring in the theoretical treatments would be reduced by an accurate consideration of Debye shielding is shown to be unjustified. It is further shown that if the model forming the basis of their arguments is adequately amended and correctly exploited, the well-known results of the unified and impact theories are recovered.