  To meet the challenges of high-resolution molecular spectroscopy,
increasingly sophisticated spectroscopic techniques were developed. For a long
time FTIR and laser-based spectroscopies were used for these studies. The
recent development of dual-comb spectroscopy at high-resolution makes this
technique a powerful tool for gas phase studies. We report on the use and
characterization of the IRis-F1, a tabletop mid-infrared dual-comb
spectrometer, in the newly developed step-sweep mode. The resolution of the
wavenumber axis is increased by step-wise tuning (interleaving) and accurate
measurement of the laser center wavelength and repetition frequency. Doppler
limited measurements of N2O and CH4 reveal a wavenumber accuracy of 1E-4 cm-1
on the covered range of > 50 cm-1. Measured half-widths of absorption lines
show no systematic broadening, indicating a negligible instrument response
function. Finally, measurements of nitrogen pressure broadening coefficients in
the v4 band of methane show that quantum cascade laser dual-comb spectroscopy
in step-sweep mode is well adapted for measurements of precision spectroscopic
data, in particular line shape parameters.
