2000ApJS..126..469H

Motivated by the question of the importance of ionization stratification in solving the ``momentum problem'' of Wolf-Rayet stellar winds, we have chosen a sample of 14 WN stars for a systematic study. We performed measurements of the emission line widths on ultraviolet, optical, and infrared spectra to obtain data spanning a large range of ionization potentials. We provide extensive tables of these measurements as well as line profile classifications. The presence of ionization stratification in the wind should result in a correlation between ionization potential and line width. We find most of the winds to be stratified and discuss the level of stratification found in each star. To test the importance of ionization stratification to efficient radiation-to-wind momentum transfer, we compare our empirically measured stratification strengths with two sets of theoretical performance numbers and give the correlation statistics in each case.