Abstract
We have measured the positron mobility μ in a sample of scintillation grade anthracene at two temperatures. We obtain at 300 K: μ=(26.0±0.9±2.6) cm2V−1s−1 and at 77 K: μ=(33.4±1.1±3.3) cm2V−1s−1, where the first error estimate is statistical and the second is systematic. We have also made preliminary measurements on a highly purified sample that yields μ=(130±3±20) cm2 V−1 s−1 at 300 K. The data are consistent with the hypothesis that the positron is scattered from both impurities and acoustic phonons in the first sample, and predominantly from photons in the second. It appears that positrons in pure anthracene crystals are delocalized and have a mean free path of about 85 Å at room temperature.
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