Spectral properties from Lyα to Hα for an essentially complete sample of quasars.: I.: Data

We have obtained quasi-simultaneous ultraviolet-optical spectra for 22 out of 23 quasars in the complete Palomar-Green X-ray sample with redshift z < 0.4 and M-B < -23. The spectra cover rest-frame wavelengths from at least Ly alpha to H alpha. Here we provide a detailed description of the data, including careful spectrophotometry and redshift determination. We also present direct measurements of the continua, strong emission lines, and features, including Ly alpha, Si IV + O IV] lambda 1400, C IV, C III], Si III], Mg II, H beta, [O III], He I lambda 5876 + Na I lambda lambda 5890,5896, H alpha, and blended iron emission in the UV and optical. The widths, asymmetries, and velocity shifts of profiles of strong emission lines show that C IV and Ly alpha are very different from H beta and H alpha. This suggests that the motion of the broad-line region is related to the ionization structure, but the data appear to not agree with the radially stratified ionization structure supported by reverberation mapping studies, and therefore suggest that outflows contribute additional velocity components to the broad emission line profiles.