Scintillation Response of Anthracene to 6-30 keV Photoelectrons

Observations have been made of the scintillation response S of a 0.2 cm thick anthracene crystal to photoelectrons of energy E =6 to 30keV produced by various characteristic K X-rays. The responses to 114 In and 137 Cs internal conversion electrons were also measured, and the results reduced to a standard scale of S , and compared with other data. The ( S, E ) curve agrees closely with that predicted theoretically. The response curve at -65°C is identical with that at 16°C, apart from a general increase of 50% in S . The response to internal electrons is significantly greater than that to external electrons of the same low energy. Reasons are suggested for the divergent results reported by Robinson and Jentschke. The reduced response to external electrons is attributed to the escape and/or quenching of the fluorescence excitation energy at the crystal surface. These and other surface phenomena affecting the response of organic scintillators to short-range external particles are discussed.