Radio recombination line spectrum for W3(OH), shown as flux density versus LSR radial velocity (solid line). The dashed line shows the least-squares fit to the spectrum. The continuum has been subtracted with a linear fit. We have no data for the 11.1 to 62.8 km s^-1 radial velocity range, and we have interpolated the spectrum for this region with a straight line. The parameters of the recombination lines are given in Table 1.