Diffuse Interstellar Bands and the Ultraviolet Extinction Curves: The
  Missing Link Revisited
  A large number of interstellar absorption features at ~ 4000\AA\ -- 1.8
{\mu}m, known as the "diffuse interstellar bands" (DIBs), remains unidentified.
Most recent works relate them to large polycyclic aromatic hydrocarbon (PAH)
molecules or ultrasmall carbonaceous grains which are also thought to be
responsible for the 2175 \AA\ extinction bump and/or the far ultraviolet (UV)
extinction rise at $\lambda^{-1} > 5.9\ {\mu}m^{-1}$. Therefore, one might
expect some relation between the UV extinction and DIBs. Such a relationship,
if established, could put important constraints on the carrier of DIBs. Over
the past four decades, whether DIBs are related to the shape of the UV
extinction curves has been extensively investigated. However, the results are
often inconsistent, partly due to the inconsistencies in characterizing the UV
extinction. Here we re-examine the connection between the UV extinction curve
and DIBs. We compile the extinction curves and the equivalent widths of 40 DIBs
along 97 slightlines. We decompose the extinction curve into three Drude-like
functions composed of the visible/near-infrared component, the 2175 \AA\ bump,
and the far-UV extinction at $\lambda^{-1} > 5.9\ {\mu}m^{-1}$. We argue that
the wavelength-integrated far-UV extinction derived from this decomposition
technique best measures the strength of the far-UV extinction. No correlation
is found between the far-UV extinction and most (~90\%) of the DIBs. We have
also shown that the color excess E(1300-1700), the extinction difference at
1300 \AA\ and 1700 \AA\ often used to measure the strength of the far-UV
extinction, does not correlate with DIBs. Finally, we confirm the earlier
findings of no correlation between the 2175 \AA\ bump and DIBs or between the
2175 \AA\ bump and the far-UV extinction.
