Far-ultraviolet extinction and diffuse interstellar bands

We relate the equivalent widths of the major diffuse interstellar bands (DI Bs) near 5797 and 5780 Angstrom with different colour excesses, normalized by E(B - V), which characterize the growth of interstellar extinction in di fferent wavelength ranges. It is demonstrated that the two DIBs correlate b est with different parts of the extinction curve, and the ratio of these di ffuse bands is best correlated with the far-ultraviolet (UV) rise. A number of peculiar lines of sight are also found, indicating that the carriers of some DIBs and the far-UV extinction can be separated in certain environmen ts, e.g. towards the Per OB2 association.