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

作者：Brumfield Brian E^*; Stewart Jacob T; Weaver Susanna L Widicus; Escarra Matthew D; Howard Scott S; Gmachl Claire F; McCall Benjamin J

来源：Review of Scientific Instruments, 2010, 81(6): 063102.

DOI：10.1063/1.3427357

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 (C(60)). As a first test of the system, high resolution spectra of the nu(8) vibrational band of CH(2)Br(2) have been acquired at similar to 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 CH(2)Br(2) 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 x 10(-8) cm(-1). Spectral simulations of the band indicate that the supersonic source produces rotationally cold (similar to 7 K) molecules.

• 出版日期2010-6