Photoluminescence of F-aggregate centers in thermal neutron irradiated LiF TLD-100 single crystals

On excitation with 445 nm light, thermal neutron and gamma-ray irradiated thermoluminescent dosimetry (TLD) grade LiF TLD-100 single crystals exhibit green photoluminescence (PL) emission with a peak around 521 nm characteristic of F-3(+) centers and a red PL emission peaking around 656 nm characteristic of F-2 centers. At low dose levels, the 515 to 653 nm PL intensity ratio for thermal neutrons is nearly three times higher when compared to that for gamma-rays. The results are discussed on the basis of the trap structures of these two defect centers and microdosimetric concepts. The integrated PL emission from 460 to 600 nm increases nearly linearly between 10(10) and 10(13) n cm(-2). On a dose equivalent basis, the intensity of this PL is nearly 1350 times stronger for thermal neutrons than for Co-60 gamma-rays.