Diffuse bands 9577 and 9633 -- relations to other interstellar features
  We study, for the first time, the relations of two strong diffuse bands
(DIBs) at 9633 and 9577~\AA, commonly attributed to C$_{60}^+$, to other
interstellar features seen in optical and UV spectra including H{\sc i}, Ca{\sc
i}, Fe{\sc ii}, Na{\sc i}, Ti{\sc ii}, CN, CH, CH$^+$, and C$_2$ and DIBs 5780,
5797, 6196, 6269, 6284, and 6614. We analyzed 62 lines of sight where the
stellar contamination by Mg{\sc ii} was corrected or found negligible for DIB
9633. Equivalent widths of DIB 9577 were measured in 62 lines of sight. Poor
mutual correlation between the strengths of the above features and the major
diffuse bands (5780 and 5797) as well as with other DIBs (with some exceptions)
were revealed. The considered DIBs are also poorly correlated with the features
of neutral hydrogen, molecular carbon, and those of simple interstellar
radicals. Perhaps this phenomenon can be explained if the diffuse band 9577 is
an unresolved blend of two or more interstellar features. There are indications
that 9633 and 9577 diffuse bands are stronger in $\sigma$-type clouds, i.e.
these features resemble the behavior of reasonably broad DIBs, which are strong
in the lines of sight where the UV flux from the very hot nearby stars plays an
important role.
