Exciton dynamics in $alpha$-particle tracks in organic crystals: magnetic field study of the scintillation in tetracene crystals

Journal Article · Sat Nov 15 04:00:00 EST 1975 · Phys. Rev., B, v. 12, no. 10, pp. 4113-4134

OSTI ID:4113699

Geacintov, N E; Binder, M; Swenberg, C E; Pope, M

The mechanisms of scintillation of organic crystals bombarded by $alpha$ particles are discussed in terms of the current knowledge of exciton dynamics, which has been derived from a study of the photofluorescence of crystals such as anthracene and tetracene. The scintillation of tetracene excited by 4.4-MeV $alpha$ particles incident in a direction perpendicular to the ab plane has been studied in the presence of external magnetic fields (0 to 4000 G) and compared with the scintillation of crystalline anthracene. At 298$sup 0$K, the magnetic field effect on the total scintillation yield is (+2.5 +- 0.5) percent in tetracene and displays a typical fissionlike (fission of one singlet exciton into two triplets) dependence. At low temperatures when fission is suppressed, a fusionlike dependence (reverse of fission) appears with a (-4 to -5) percent effect at 4000 G at 148$sup 0$K. In anthracene, the fusionlike dependence is observed with a (-4 to -5) percent effect at 4000 G at 148$sup 0$K. In anthracene, the fusionlike dependence is observed at all temperatures in the range studied (148 to 298$sup 0$K). Using appropriate kinetic equations, expressions are derived for the prompt (L/sub P) and delayed (L/sub D/) components of the total scintillation yield L = L/sub P/ + L/sub D/. These expressions describe the temperature and magnetic field dependence of L, which arises because of the temperature and magnetic field dependence of the exciton fission and fusion rate constants in tetracene. In tetracene, L/sub D/ appears to be strongly temperature dependent, while L/sub P/ is not. This is explained in terms of the high density of transient singlet exciton quenchers in the $alpha$-particle track. The density of these transient quenchers is estimated to be in the range of 3 x 10$sup 17$--5 x 10$sup 18$ cm$sup -3$, and they are identified, in accord with a previous suggestion by Schott, as triplet excitons which are created by random recombination of electrons and holes in the $alpha$- particle track. (auth)

• Research Organization: New York Univ., NY
• NSA Number: NSA-33-017891
• OSTI ID: 4113699
• Journal Information: Phys. Rev., B, v. 12, no. 10, pp. 4113-4134, Journal Name: Phys. Rev., B, v. 12, no. 10, pp. 4113-4134; ISSN PLRBA
• Country of Publication: United States
• Language: English

Related Subjects

*TETRACENE-- CHEMICAL RADIATION EFFECTS
360605* --Materials--Other Materials--Radiation Effects
ALPHA BEAMS
ALPHA PARTICLES
ANTHRACENE
CRYSTALS
EXCITONS
MAGNETIC FIELDS
MEDIUM TEMPERATURE
MEV RANGE 01- 10
N40300 --Chemistry--Radiation Chemistry
N50340* --Metals
Ceramics
& Other Materials--Plastics & Other Materials--Radiation Effects
PARTICLE TRACKS
PHOTOLUMINESCENCE
SCINTILLATIONS