High-resolution CO-laser sideband spectrometer for molecular-beam optothermal spectroscopy in the 5-6.6 mu m wavelength region

We have set up a new CO-laser sideband spectrometer for high-resolution mol ecular-beam optothermal spectroscopy in the mid infrared. By mixing CO-lase r lines with tunable microwave radiation, a spectral coverage of about 50% is achieved. Using a microwave resonator, a typical output power of 3 mW is realized in the region of 5-6.6 mu m (1500-2000 cm(-1)). The resolution in our molecular-beam apparatus with optothermal detection is 2.8 MHz (full w idth at half maximum). The new setup allowed the observation of the first h igh-resolution rotationally resolved spectrum of formic acid dimer (HCOOH)( 2). (C) 1999 American Institute of Physics. [S0034-6748(99)02204-2].