Absolute absorption and fluorescence measurements over a dynamic range of 10$^6$ with cavity-enhanced laser-induced fluorescence

TL;DR

This paper introduces a novel cavity-enhanced laser-induced fluorescence (CELIF) technique that combines fluorescence and ring-down methods to measure absolute absorption over a dynamic range of 10^6, improving sensitivity and accuracy.

Contribution

The paper presents the development and validation of CELIF, a new method that extends dynamic range and enhances measurement quality for absolute absorption and fluorescence.

Findings

Dynamic range extended from 10^3 to 10^6

Improved signal-to-noise ratio with cavity enhancement

Accurate determination of absorption cross sections and quantum yields

Abstract

We describe a novel experimental setup that combines the advantages of both laser-induced fluorescence and cavity ring-down techniques. The simultaneous and correlated measurement of the ring-down and fluorescence signals yields absolute absorption coefficients for the fluorescence measurement. The combined measurement is conducted with the same sample in a single, pulsed laser beam. The fluorescence measurement extends the dynamic range of a stand-alone cavity ring-down setup from typically three to at least six orders of magnitude. The presence of the cavity improves the quality of the signal, in particular the signal-to-noise ratio. The methodology, dubbed cavity-enhanced laser-induced fluorescence (CELIF), is developed and rigorously tested against the spectroscopy of 1,4-bis(phenylethynyl)benzene in a molecular beam and density measurements in a cell. We outline how the method can be utilised to determine absolute quantities: absorption cross sections, sample densities and fluorescence quantum yields.