Heteronuclear diatomics in diffuse and translucent clouds
  Diffuse and translucent molecular clouds fill a vast majority of the
interstellar space in the galactic disk being thus the most typical objects of
the Interstellar Medium (ISM). Recent advances in observational techniques of
modern optical and ultraviolet spectroscopy led to detection of many features
of atomic and molecular origin in spectra of such clouds. Molecular spectra of
heteronuclear diatomic molecules, ie. OH, OH+, CH CH+, CN, NH, CO play an
important role in understanding chemistry and physical conditions in
environments they do populate. A historical review of astronomical observations
of interstellar molecules is presented. Recent results based on visual and
ultraviolet observations of molecular features in spectra of reddened, early
type OB-stars are presented and discussed. Appearance of vibrational-rotational
spectra with observed transitions based on high-quality spectra, are also
presented. Relations between column densities of heteronuclear diatomics (based
on the recommended oscillator strengths) and intensities of diffuse
interstellar bands (DIBs) are also presented and discussed.
