Remarks on the Process of Carrier Generation in Electron-Bombarded Crystalline Anthracene

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Abstract
Secondary emission results show that the energy needed to create an electron-hole pair by low-energy electron bombardment of anthracene crystals is less than 75 eV, and that the thermalization distance of a secondary is such that initial recombination cannot account for the low yield of one pair per 400 eV obtained by Delany and Hirsch. It is suggested that columnar recombination accounts for at least part of the difference. Preliminary results of characteristic losses of 41 keV electrons in anthracene are reported. The dominant loss, in the range 14–25 eV, is a solid state effect, tentatively assigned to collective oscillations of the π electrons. The free path for excitation of these oscillations by low-energy electrons should be very short and electron-hole pair creation would proceed largely through ionization of these plasmons. The small value of the pair-creation energy suggests that radiative recombination inside a column could play a large role in fast scintillation processes in anthracene.