Incoherent broad-band cavity-enhanced absorption spectroscopy of liquids

A new application of incoherent broad-band cavity enhanced absorption spectroscopy (IBBCEAS) to weak transitions in solution through a very straightforward modification of commercially available double-beam UV/VIS absorption spectrometers is reported. The improved sensitivity of the new approach is demonstrated on basis of the weak Franck-Condon inhibited absorption of the fifth C-H stretch overtone in liquid benzene. The theoretical limits of the enhancement of the signal-to-noise ratio of IBBCEAS in comparison with single pass absorption experiments are discussed for a set of given experimental cavity parameters. The optical loss properties of a typical transparent cuvette window in the cavity are also discussed.