Spontaneous emission rates of single impurity molecules in birefringent crystals

We have developed a theory of the dependence of the spontaneous emission rate and, consequently, the radiative line width of a single impurity molecule on the orientation of the transition dipole moment vector in birefringent biaxial host crystal. The calculations for seven biaxial host crystals (naphthalene, anthracene, terphenyl, phenanthrene, fluorine, chrysene, and diphenyl) show that the spontaneous emission rate depends strongly on the orientation of the transition dipole moment vector with respect to the principal axes of the host crystal and has only a weak dependence on the chemistry of the host.