Effect of Magnetic Field on the Fluorescence of Tetracene Crystals: Exciton Fission

Abstract

The fluorescence efficiency of tetracene single crystals may be enhanced by as much as 38% in a magnetic field $H>2000$ G. The enhancement is anisotropic with respect to the orientation of $H$ in the $\mathrm{ab}$ plane. It is shown that a magnetically sensitive coupling of singlet states to a double-triplet-exciton state (${T}_{1}{T}_{1}$) at \ensuremath{\sim}2.40 eV is an important channel for radiationless decay in crystalline tetracene above 160\ifmmode^\circ\else\textdegree\fi{}K.