Magnetic Field Modulated Scintillation from Tetracene‐Doped Anthracene Crystals under α‐Particle Irradiation

It is measured the effect of magnetic fields on the scintillation of tetracene‐doped anthracene crystals under α‐particle bombardment. Comparing the data with results obtained under photo‐excitation yields a lower bound for the average triplet exciton density in an α‐particle track. The present calculated value of 3 × 10¹⁷ triplets cm⁻³ is in good agreement with a previous estimate of 10¹⁸ cm⁻³ for pure tetracene. It is also shown that under α‐particle bombardment, because of the high triplet exciton density, heterofusion of a free anthracene triplet exciton with a trapped tetracene triplet is not an important channel for producing scintillation. Instead, most of the green tetracene scintillation arises from the trapping of anthracene singlet excitons, which in turn are produced by the homofusion of host triplets.