GENERALIZED OSCILLATOR STRENGTH FOR THE B-1(3U)[-(1)A(G) TRANSITION OF ANTHRACENE, AS DETERMINED BY ELECTRON-ENERGY-LOSS SPECTROSCOPY

As part of a systematic quantitative study of the angular dependence o f valence-shell electron-impact excitation of molecules, we have deter mined, for the first time, the absolute inelastic differential cross s ection and the generalized oscillator strength (GOS) for the B-1(3u) < -- (1)A(g) transition (5.2 eV) in anthracene (C14H10). A minimum in th e GOS has been observed at a K-2 value of around 0.2 au. The GOS value s were determined from the relative inelastic differential cross secti on, measured with an electron-impact spectrometer, which uses a Wien-f ilter velocity analyser. The incident electron energy was 1 keV, the e nergy resolution was 1.0 eV and the energy-loss spectra were obtained in the range of 1.75 degrees-6.75 degrees. The absolute elastic differ ential cross section was determined in the 0.5 degrees-20 degrees angu lar range.