A survey of Be stars in the infrared. II. Determination of envelope dimensions

We describe plate material concerning 34 Be stars in the λλ 8309-8791 region observed at the OHP Observatory at 33 A. mm-1 dispersion. We summarize the descriptions of these stars, complemented by those of paper I. As a result we can base our conclusions upon almost 70 objects, which constitutes the largest sample so far observed in this spectral region. Emissions are frequent in all Be stars, but are more concentrated in early-type (<B5) stars. The same phenomenon is found for the Ca II emissions; here we notice a positive correlation of Ca II emission and large infrared excesses measured with the IRAS satellite. Also the O I and N I emissions are more frequent in early-type stars. We have also analysed the emission line structure based upon the equivalent widths, half widths and emission peak separations of a large number of lines. We have determined the outer radii of the emission region and find them to lie between 2 and 4 stellar radii. As for the internal radius, it lies close to the stellar surface, for all lines