Enhancement of Absorption Spectra by Dye-Laser Quenching, II*

Abstract

Insertion of samples into a broad-band dye-laser cavity enhances photographic detectability of trace absorptions by approximately three orders of magnitude. Optical densities as small as 0.0004 were readily detected in a dilute solution of Eu(NO₃)₃. In a modified technique the bandwidth of the dye laser was reduced by using prisms, and the wavelength of this narrow band was swept through the absorption. The modified technique permitted detection of optical densities as small as 0.01. Solutions of theoretical equations describing both processes give good agreement with experimental results, and they provide insight into the mechanism of the effect. The measurements with the broad-band laser could be made in 100 ns or less; therefore, this technique should provide a powerful tool for detection of short-lived transients in very small concentrations.