Trapping of radiation in a laser ablated YBa2Cu3O7 plume

A tunable dye laser has been used to selectively photo-hump transitions in a laser ablated YBa2Cu3O7 plume. The resultant fluorescence and scattered light has been monitored both with a photo-multiplier tube and a gated intensified CCD array camera. The spatial and temporal characteristics of the fluorescence are used to demonstrate that phonons emitted within the plume are strongly reabsorbed, and thus radiation is effectively trapped. Measurement of the degree of trapping is limited due to an alternative radiative decay channel, but a maximum escape probability of about 10% can be inferred, even several centimeters from the target surface, and more than 10 mu s after the initial ablation pulse. The implications for plasma spectroscopy and laser induced fluorescence studies of ablated plumes are discussed. (C) 1996 American Institute of Physics.