Charge carrier generation in p-terphenyl crystal. Autoionization of higher excited states

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Abstract
Photoionization of singlet excitons in p‐terphenyl crystal is studied with nanosecond laser excitation. The photoionization spectrum and the photoabsorption spectrum of the lowest excited state are measured. The ratio of the two spectra gives the efficiency with which higher excited states, generated by the two‐step excitation, ionize. The observed efficiency is constant below 7.3 eV and is remarkably high (∼10−2 ). The results do not support the view that the excess energy is converted directly to the kinetic energy of the generated electrons in the crystal and indicate that the initially prepared higher excited states relax rapidly and the succeeding autoionization yields electrons with a fixed kinetic energy.