We develop a perturbation theory for the lifetime and emission intensity for isolated resonances in asymmetric resonant cavities. The inverse lifetime $\Gamma$ and the emission intensity $I\left(\theta \right)$ in the open system are expressed in terms of matrix elements of operators evaluated with eigenmodes of the closed resonator. These matrix elements are calculated in a semiclassical approximation which allows us to represent $\Gamma$ and $I\left(\theta \right)$ as sums over the contributions of rays which escape the resonator by refraction.

• Received 8 July 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.4991