TITLE

A quantum cascade laser cw cavity ringdown spectrometer coupled to a supersonic expansion source

AUTHOR(S)
Brumfield, Brian E.; Stewart, Jacob T.; Widicus Weaver, Susanna L.; Escarra, Matthew D.; Howard, Scott S.; Gmachl, Claire F.; McCall, Benjamin J.
PUB. DATE
June 2010
SOURCE
Review of Scientific Instruments;Jun2010, Vol. 81 Issue 6, p063102
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
A new instrument has been constructed that couples a supersonic expansion source to a continuous wave cavity ringdown spectrometer using a Fabry–Perot quantum cascade laser (QCL). The purpose of the instrument is to enable the acquisition of a cold, rotationally resolved gas phase spectrum of buckminsterfullerene (C60). As a first test of the system, high resolution spectra of the ν8 vibrational band of CH2Br2 have been acquired at ∼1197 cm-1. To our knowledge, this is the first time that a vibrational band not previously recorded with rotational resolution has been acquired with a QCL-based ringdown spectrometer. 62 transitions of the three isotopologues of CH2Br2 were assigned and fit to effective Hamiltonians with a standard deviation of 14 MHz, which is smaller than the laser frequency step size. The spectra have a noise equivalent absorption coefficient of 1.4×10-8 cm-1. Spectral simulations of the band indicate that the supersonic source produces rotationally cold (∼7 K) molecules.
ACCESSION #
51848951

 

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