Infrared amplified spontaneous emission from the 0 ((3)P0) and 0 ((1)D2) ion-pair states of molecular bromine.

We report the observation of amplified spontaneous emission for the first time from the 0 ((3)P0) and 0 ((1)D2) ion-pair states of Br2 by using an optical-optical double resonance technique through the B (3)Π(0) valence state as the intermediate state. The strong infrared emission propagating along the incident laser radiation is assigned to the parallel ASE transitions from the 0 ion-pair states down to the nearby 0 ion-pair states. The subsequent UV fluorescence from the 0 states to the high vibrational levels of the ground state is also observed. By the Franck-Condon simulation of the cascade UV fluorescence, we determine the vibrational distributions in the 0 states populated by ASE, which are consistent with the intensity distribution in the dispersed infrared ASE spectrum. The lifetimes of the relevant ion-pair states are evaluated by analyzing the temporal profiles of the UV fluorescence.