Time resolved simultaneous detection of 14NO and 15NO via mid-infrared cavity leak-out spectroscopy |
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Authors: | Halmer Daniel von Basum Golo Horstjann Markus Hering Peter Mürtz Manfred |
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Institution: | Institut für Lasermedizin, Heinrich-Heine-Universit?t Düsseldorf, Universit?tsstr. 1, 40225, Düsseldorf, Germany. |
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Abstract: | We present a ring-down absorption spectrometer based on a continuous-wave CO laser in the mid-infrared spectral region near lambda = 5 microm. Using a linear ring-down cavity (length: 0.5 m) with high reflective mirrors (R = 99.988 %), we observed a noise-equivalent absorption coefficient of 3 x 10(-10) cm(-1)Hz(-1/2). This corresponds to a noise-equivalent concentration of 800 parts per trillion (ppt) for (14)NO and 40 ppt for (15)NO in 1 s averaging time. We achieve a time resolution of 1 s which allows time resolved simultaneous detection of the two N isotopes. The delta(15)N value was obtained with a precision of +/-1.2 per thousand in a sample with a NO fraction of 11 ppm. The simultaneous detection enables the use of (15)NO as a tracer molecule for endogenous biomedical processes. |
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