Improving the accuracy and precision of broadband optical cavity measurements

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Fig. S1. Optical and sample handling configuration of the LED IBBCEAS instrument
Chen, Jun
Fullam, Donovan P.
Yu, Shuaishuai
Böge, Olaf
Le, Phuoc Hoa
Herrmann, Hartmut
Venables, Dean S.
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Elsevier B.V.
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Most extinction measurements require a stable light source to attain high precision and accuracy. Here, we present a convenient approach to normalize light source intensity in broadband optical cavity measurements. In the absence of sample extinction, we show that the in-band signal – the high finesse spectral region of the optical cavity in which sample extinction is measured with high sensitivity – is strongly correlated with the out-of-band signal. The out-of-band signal is insensitive to sample extinction and can act as a proxy for light source intensity. This normalization approach strongly suppressed in-band intensity changes in two incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) instruments with dissimilar light sources and optical cavity properties. Intensity fluctuations in an arc lamp system were suppressed by a factor of 7 to 16 and in the LED spectrometer by a factor of 10. This approach therefore improves the accuracy and precision of extinction measurements where either property is limited by the light source stability.
Normalization , Broadband optical cavity , Atmospheric , UV/visible , Aerosol , Gases
Chen, J., Fullam, D. P., Yu, S., Böge, O., Le, P. H., Herrmann, H. and Venables, D. S. (2019) 'Improving the accuracy and precision of broadband optical cavity measurements', Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 218, pp. 178-183. doi: 10.1016/j.saa.2019.04.015