Excited singlet absorption in blue laser dyes: Measurement by picosecond flash photolysis

Absorption from the lowest relaxed excited singlet state in the laser dyes POPOP, carbostyril 165, 4-methylumbelliferone, 7-diethylamino-4-trifluoromethylcoumarin, and coumarin 30 has been measured over the range, approximately, from 350 to 650 nm. In addition, rhodamine 6G was remeasured to permit comparison of our procedures with previous work and to help promote the emergence of a standard substance which all laboratories may use to test and refine their procedures. For comparison, 9,10-diphenylanthracene was investigated as an example of an "unsuccessful laser dye." Measurements were made using excitation pulses of 40 ps duration at 347 nm and a continuum probe, of the same duration, delayed by 200 ps.