Anomalous fluorescence of ensembles of optical centers in an intense laserpump field

Anomalous laser-induced fluorescence of solutions of polyatomic molecules e xcited with intense laser radiation of subnano- or picosecond duration is s tudied. The condensation of fluorescence in the pump field is observed for the first time. The effect shows itself as an approach of the fluorescence kinetics to the pump pulse kinetics and an increase in quantum yield with i ncreasing excitation power density. The experimental data are analyzed in t erms of four-wave cooperative interaction in the system formed by an ensemb le of optical centers and the pump field and involving zero-point vacuum vi brations, which are assumed to he partially locally coherent.