17 May 2012 Fourier transform infrared phase shift cavity ring down spectrometer
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OPTRA has developed a novel approach to phase shift cavity ring down spectroscopy (PS-CRDS) using a Fourier transform infrared (FTIR) modulator to impose the spectrally-dependent amplitude modulation on a broadband IR light source. As with previous PS-CRDS measurements, we excite a resonant cavity with amplitude modulated energy and measure the phase shift of the modulated signal exiting the cavity which is proportional to the ring down time and inversely proportional to the losses of the cavity including those due to molecular absorption. In contrast to previous efforts, we impose the amplitude modulation with the FTIR interferometer instead of an external electro-optical modulator and extract the phase from each interferogram thereby enabling broadband FTIR-PS-CRDS measurements at greater than 1 Hz update rates. The measured phase spectra can then be used for multicomponent analysis. The combined measurement can be viewed as a resonant cavity enhancement to traditional FTIR spectroscopy or a broadband enhancement to CRDS. In our paper we present the theory behind this measurement and describe the breadboard and test results from our feasibility study.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Julia Rentz Dupuis, Julia Rentz Dupuis, James R. Engel, James R. Engel, } "Fourier transform infrared phase shift cavity ring down spectrometer", Proc. SPIE 8374, Next-Generation Spectroscopic Technologies V, 837410 (17 May 2012); doi: 10.1117/12.917318; https://doi.org/10.1117/12.917318

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