---
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.'
author:
- 'Scott E. Sanders'
- 'Oliver R. Willis'
- 'N. Hendrik Nahler'
- Eckart Wrede
title: 'Absolute absorption and fluorescence measurements over a dynamic range of 10$^\textbf{6}$ with cavity-enhanced laser-induced fluorescence'
---

Introduction {#sec:intro}
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Laser-induced fluorescence (LIF) has become a well established spectroscopic technique since the advent of the laser.[@Donovan2007; @Kinsey1977; @Zare2012] It is an indirect absorption 