ABSORPTION-SPECTRUM OF NEAT LIQUID BENZENE AND ITS CONCENTRATED-SOLUTIONS IN N-HEXANE FROM 220 TO 170 NM

The electronic absorption spectrum of benzene has been obtained by pho totransmission measurements over a concentration range from 0.005 M in n-hexane to the neat liquid at 11.2 M and over a spectral range that extends down to 170 nm. Good agreement is obtained with previously rep orted measurements on the neat Liquid. The oscillator strength of the strongly allowed A(1g) --> E(1u) transition is maintained at ca. 1.0 a s the benzene concentration increases but is accompanied by extensive redistribution of the intensity such that the optical cross section at the position of the absorption maximum (which shifts from 184.(2) nm in dilute solution to 189.(5) nn in the neat liquid) reduces by a fact or of 2.7. An explanation for these changes in terms of Lorentz field corrections to the complex dielectric constant is developed, and its i mplication to the assignment of the neat Liquid absorption as a collec tive excitation is considered.