The plasma-broadened ${\mathrm{H}}_{\alpha }$ and ${\mathrm{H}}_{\beta }$ spectral-line profiles of hydrogen were calculated retaining the time ordering in the $S$ matrices of the width-shift operator by diagonalizing with the O(4) group. Significant changes occur: The ${\mathrm{H}}_{\alpha }$ peak is decreased 15%, the half-width is increased 25%, and the ${\mathrm{H}}_{\beta }$ relative dip is decreased 23% without significant alteration of the maximum intensity of half-width. Agreement with experiment is improved appreciably.

• Received 3 February 1975

DOI:https://doi.org/10.1103/PhysRevLett.34.785