HIGH-RESOLUTION SPECTROSCOPY OF THE $\nu_8$ BAND OF METHYLENE BROMIDE USING A QUANTUM CASCADE LASER-BASED CAVITY RINGDOWN SPECTROMETER
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Date
2010
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Ohio State University
Abstract
Our group has constructed a cavity ringdown spectrometer based on a quantum cascade laser (QCL) in an effort to obtain a high-resolution gas phase spectrum of buckminsterfullerene (C$_{60}$). To test the performance of our spectrometer we have observed the $\nu_8$ band of methylene bromide (CH$_2$Br$_2$) from 1196 to 1197.5 cm$^{-1}$. This band had previously only been recorded at low resolution. Cold methylene bromide molecules were produced in a continuous supersonic expansion from a 700 $\mu$m pinhole and probed using continuous wave cavity ringdown spectroscopy (cw-CRDS). To our knowledge, this is the first experiment to measure a supersonic jet-cooled sample using a QCL-based cw-CRDS spectrometer. We have assigned the observed ro-vibrational lines from the three isotopomers of CH$_2$Br$_2$ to effective Hamiltonians, and find that the molecules have been cooled to a rotational temperature of $\sim$3--10 K.
Description
Author Institution: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801; Department of Electrical Engineering, Princeton University, Princeton Institute for the Science and Technology of Materials, Princeton, NJ 08544; Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801