EFFECTS OF HIGH PRESSURE UPON THE NEAR ULTRAVIOLET ABSORPTION SPECTRA OF THE $POLYACENES^{*}$

$^{*}$This work was supported in part by the Office of Scientific Research, Air Research and Development Command, under Contract Nol AF 18 (600)- 430.""Author Institution: Departments of Physics and Chemistry, The University of TexasThe absorption spectra of naphthalene, anthracene, and napthacene in n-pentane have been recorded in the near ultraviolet at pressures up to 5500 bars. The wavelength of absorption increases linearly with the dielectric constant of the pressurized solvent, $\lambda=\frac{\Delta\lambda}{\Delta{K}}({K}-1)+\lambda_{o}=\frac{\Delta\lambda}{\Delta{K}}$ varies from 26 A for the naphthalene $^{1}{A}_{1{g}}-^{1}{B}^{-}_{3{u}}$ transition to 235 A for the naphthacene $^{1}{A}_{1{g}}^{-}-^{1}{B}^{+}_{2{u}}$ transition. Since $\Delta\lambda/\Delta{K}$ can be accurately measured, a practical method exists for distinguishing between transitions. Values of $\lambda_{o}$ obtained by extrapolating to K = 1 are within a few angstroms of the measured values that are obtainable for the vapor state. $\frac{1}{\lambda_{o}}\frac{\Delta\lambda}{\Delta {K}}$ increases generally with the oscillator strength of the transition as is predicted by theory. However, no simple relation exists between slope and oscillator strength