Properties of Diffuse Interstellar Bands at Different Physical
  Conditions of the ISM
  Diffuse interstellar bands (DIBs) can trace different conditions of the ISM
along the sightline toward the observed stars. A small survey was made in
optical wavelengths, producing high resolution and high signal to noise
spectra. We present measurements of 19 DIBs' properties in 50 sightlines
towards hot stars, distributed at a variety of galactic coordinates and
interstellar reddening. Equivalent widths were obtained by fitting asymmetric
Gaussian and variable continuum to DIBs. Conditions of the ISM were calculated
from 8 atomic and molecular interstellar lines. Two distinctively different
types of DIBs were identified, by carefully comparing correlation coefficients
between DIBs and reddening and by different behaviour in UV shielded ($\zeta$)
and non-shielded ($\sigma$) sightlines. A ratio of DIBs at 5780 \AA\ and~5797
\AA\ proved to be reliable enough to distinguish between two different
sightline types. Based on linear relations between DIB equivalent width and
reddening for $\sigma$ and $\zeta$ sightlines, we divide DIBs into type {\sc i}
(where both linear relations are similar) and type {\sc ii} (where they are
significantly different). Linear relation for $\zeta$ type sightlines always
show a higher slope and larger x-intercept parameter than the relation for
$\sigma$ sightlines. Scatter around the linear relation is reduced after the
separation, but it does not vanish completely. This means that UV shielding is
the dominant factor of the DIB equivalent width vs.\ reddening relation shape
for $\zeta$ sightlines, but in $\sigma$ sightlines other physical parameters
play a major role. No similar dependency on gas density, electron density or
turbulence was observed. A catalog of all observed interstellar lines is made
public.
