The diffuse interstellar bands. IV - The region 4400-6850 A

It is shown that 39 diffuse bands lying between 4400 and 6850 A can be regarded as certainly or probably interstellar bands. Of these, 24 bands are described in detail. These, and seven additional features which may be interstellar are tabulated. For those 17 bands for which the data are most extensive, the correlation of equivalent width with the color excess ranges from good to excellent when regional effects and errors of observation are taken into consideration. To a good first approximation, the entire diffuse line spectrum strengthens together with and in direct proportion to increasing interstellar extinction. This result supports the hypothesis that the diffuse lines can properly be regarded as fine structure in the interstellar extinction curve.