title: Atmospheric observations of multiple molecular species using ultra-high-resolution external cavity quantum cascade laser heterodyne radiometry.
abstract: We demonstrate a widely tunable laser heterodyne radiometer operating in the thermal IR during an atmospheric observation campaign in the solar occultation viewing mode. An external cavity quantum cascade laser tunable within a range of 1120 to 1238 cm(-1) is used as the local oscillator (LO) of the instrument. Ultra-high-resolution (60 MHz or 0.002 cm(-1) transmission spectroscopy of several atmospheric species (water vapor, ozone, nitrous oxide, methane, and dichlorodifluoromethane) has been demonstrated within four precisely selected molecule-specific narrow spectral windows (∼1 cm(-1). Atmospheric transmission lines within each selected window were fully resolved through mode-hop-free continuous tuning of the LO frequency. Comparison measurements were made simultaneously with a high-resolution Fourier transform spectrometer to demonstrate the advantages of the laser heterodyne system for atmospheric sounding at high spectral and spatial resolutions.
authors.affiliation: Space Science and Technology Department, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, OX11 0QX, UK. damien.weidmann@stfc.ac.uk
authors.forename: Damien
authors.initials: D
authors.lastname: Weidmann
authors.forename: Tracy
authors.initials: T
authors.lastname: Tsai
authors.forename: Neil A
authors.initials: NA
authors.lastname: Macleod
authors.forename: Gerard
authors.initials: G
authors.lastname: Wysocki