Research Group Prof. Dr. G. Friedrichs

Mid-IR Frequency Modulation Spectroscopy

Mid-IR-FMSSeptember 2019: A first paper on the implementation of frequency modulation spectroscopy (FMS) in the mid-infrared has been published in the journal Optics Express: "M. Stuhr, N. Faßheber, G. Friedrichs; Single-tone mid-infrared frequency modulation spectroscopy for sensitive detection of transient species. Optics Express 27 (2019) 26499 - 26512. https://doi.org/10.1364/OE.27.026499." The paper, which has been selected as a highlight article by the journal editor, reports the first implementation of a Mid-IR-FM spectrometer based on external modulation with an electro-optical phase modulator. FMS is a very sensitive way to perform absorption spectroscopy and allows us to sensitively detect small molecules. A particular strength of FMS is the possibility to measure concentration-time profiles with up to nanosecond time resolution in real time (i.e., without the need to repeat the experiment with variable time delays).The new FM spectrometer will be used both for high-temperature rate constant studies of small radicals behind shock waves and the detection of intermediates in particle-forming environments such as a dusty acetylene plasma.