Delayed radioluminescence of some heterostructured organic scintillators

Abstract The processes leading to the appearance of phosphorescence and delayed fluorescence in organic molecular materials compete. This paper compares the ratio of the intensities of delayed fluorescence and phosphorescence with the pulse shape discrimination (PSD) capability of organic scintillators. The paper considers hot-pressed polycrystals and composite samples containing single-crystal organic grains as the heterostructured organic scintillators. The single crystals and heterostructured scintillators contained trans-stilbene, p-terphenyl, anthracene, and phenanthrene. Samples based on trans-stilbene and p-terphenyl at 77 K showed an intense delayed fluorescence, which appeared against the background of weak phosphorescence. It indicates the active formation of delayed fluorescence in these materials. We did not observe a similar effect for samples based on anthracene and phenanthrene. At the same time, it was the samples containing trans-stilbene and p-terphenyl grains that showed the best PSD capability at room temperature. Single-crystal and heterostructured materials containing the same scintillation substance demonstrate a close PSD capability. A comparative analysis of the intensities of delayed fluorescence and phosphorescence at low temperatures can be a method of searching for new materials that are promising for PSD problems.