Analytic formulas for frequency and size dependence of absorption and
  scattering efficiencies of astronomical polycyclic aromatic hydrocarbons
  In a series of two recent papers, the frequency and size distribution
dependence of extinction spectra for astronomical silicate and graphite grains
was analyzed by us in the context of MRN type interstellar dust models. These
grains were taken to be homogeneous spheres following the power law
$(a^{-3.5})$ size distribution which is very much in use. The analytic formulas
were obtained for the graphite and silicate grains in wavelength range 1000\AA
- 22,500\AA and their utility was demonstrated. In this paper of the series, we
present analytic formulas for the scattering and absorption spectrum of another
important constituent of interstellar dust models, namely, the polycyclic
aromatic hydrocarbons (PAHs). Relative contribution of the PAHs to extinction
{\it vis a vis} carbonaceous classical grains has been examined.
