Strong interference of luminescence of mixed modes in the neighborhood of the critical value of exciton decay

The results of a numerical calculation of the dispersion and photoluminescence spectra of mixed excitons modes of crystals CdS $(A_{n=1})$ type are analyzed depending on the decay $\Gamma$ of mechanical excitons and the angle $\theta$ of emission of radiation into vacuum in the vicinity of the critical values $\Gamma_{c}$ and $\theta_{c}$. It is shown that the mechanism $A_L$ of line formation depends significantly on the value of the light-exciton interaction parameter $\tilde{\omega}_{LT}(\theta_{c})/\Gamma_{c}$, the superposition of $M$1 and $M$2 waves with strongly asymmetric $I_{M1}(\omega)$, $I_{M2}(\omega)$, and symmetric $I_{12}(\omega)$ contours forms an almost symmetric resulting spectral contour $I(\omega)$ with a maximum at the critical frequency $\omega_{c}$.