Absolute Fluorescent Quantum Efficiency of Sodium Salicylate*

The absolute fluorescent quantum efficiency of sodium salicylate was measured by two different methods and found to be 0.99±0.03 fluorescent quanta emitted per incident ultraviolet quantum at 2537 Å. Measurements were also made at 1216 and 1611 Å by one of the methods, and the quantum efficiency was found to be 0.94 at both wavelengths. The energy conversion efficiency was found to be 0.57 at 2537 Å, 0.35 at 1611 Å, and 0.26 at 1216 Å. The angular distribution of fluorescence and the quantum efficiency were found to depend upon salicylate thickness. The quantum efficiency displays a broad maximum for thicknesses in the range 2–4 mg/cm2 and the angular distribution follows closely a cosine law in this thickness range.