The possible effect of collapse of spontaneous and stimulated emission in an ensemble of interacting molecules is predicted. It is supposed that this emission is caused by transitions between rotational levels of molecules. A molecule is modeled by a rotor nonlinearly interacting with the environment, and the dynamics of its state is theoretically investigated. For this purpose the non-linear Schrodinger equation is solved. We have obtained that under certain conditions rotor's states must change in a jump. Also, at a temperature below some limit, the Bose condensation of rotor's states can take place, so spontaneous and stimulated emission attributed to rotation of molecules can disappear in molecules at the temperature below the critical value.