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Probing Methane in Air with Infrared Sources

February 22, 2018
3:00 pm - 4:00 pm

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Dr. Hans A. Schuessler
Department of Physics and Astronomy
Professor & Chair of Optical and Biomedical Physics


High resolution spectroscopy in the infra-red has been employed for monitoring atmospheric pollution with a variety of techniques. Here we report on recent advances using broadband mid-infrared frequency combs in dual comb spectroscopy, and narrow band diode lasers in cavity ring-down and wavelength modulation spectroscopies for the detection of methane in ambient air both in our laboratory, and over km path lengths in the atmosphere. The two mid-infrared frequency combs, based on femtosecond Erbium-doped fiber oscillators, are produced through difference frequency generation with periodically poled MgO doped lithium niobate crystals and stabilized at slightly different repetition rates around 250 MHz. We performed dual frequency comb spectroscopy in the spectral range between 2900 cm-1 and 3150 cm-1 with 0.07 cm-1 resolution using a multipass cell with a path length of 580 meter. The sensitivity was about 7.6E-7 cm-1 with a data acquisition time of 80 ms. With the current setup, we measured a methane concentration of 1.9 ppmv in the ambient air in the laboratory with a minimum detection limit of 60 ppbv. In the remote sensing of greenhouse gases over long atmospheric paths carbon dioxide, methane and water vapor were the main absorbers. For these measurements a portable setup was used at the RELLIS riverside airport. The accounting for effects of atmospheric dynamics during propagating light over such large distances requires future work. This research was funded by the Robert A. Welch Foundation, Grant No. A1546 and the Qatar Foundation under Grant No. NPRP 6-465-1-091


Dr. Schuessler’s research interests lie in atomic physics and laser spectroscopy: on-line spectroscopy of short-lived isotopes, measurement of nuclear moments, spins nd charge distributions, cross-sections for spin dependent atomic collisions, ion storage spectroscopy and laser cooling, low energy ion and atom collisions, highly charged ion spectroscopy and Wigner crystals, attosecond and strong field physics, biomedical and atmospheric sensing.

Professor Schuessler attended Rupert Charles University of Heidelberg, Germany, where he earned a Ph.D. degree in physics. After two years as assistant professor at the Technological University of Berlin, he was research assistant professor and research associate professor at the University of Washington. He joined Texas A&M as associate professor in 1969 and became a professor in 1981. For short intervals, he has been visiting associate professor at the University of Washington and visiting scientist at the University of Mainz and GSI in Germany. Professor Schuessler has been collaborating on research done at CERN in Geneva, Switzerland, and currently is performing experiments at RIKEN, Wakoshi, Japan, on-line at the ISAC mass separator at TRIUMF, Vancouver Canada, and the Max-Planck-Institute for Quantum Optics at Garching, Germany. He is a member of both the American and European Physical Societies and Sigma Xi.


February 22, 2018
3:00 pm - 4:00 pm


Eller O&M Bldg., Room 807