15min:

JACOB T. STEWART, BRIAN E. BRUMFIELD, Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801; MATTHEW D. ESCARRA, CLAIRE F. GMACHL, Department of Electrical Engineering, Princeton University, Princeton Institute for the Science and Technology of Materials, Princeton, NJ 08544; BENJAMIN J. MCCALL, Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

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 (C₆₀). To test the performance of our spectrometer we have observed the ₈ band of methylene bromide (CH₂Br₂) 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 µm 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 CH₂Br₂ to effective Hamiltonians, and find that the molecules have been cooled to a rotational temperature of 3--10 K.