Optical frequency comb Fourier transform spectroscopy of 14N216O at 7.8 μm

We use a Fourier transform spectrometer based on a compact mid-infrared difference frequency generation comb source to perform broadband high-resolution measurements of nitrous oxide, (N2O)-N-14-O-16, and retrieve line center frequencies of the nu(1) fundamental band and the nu(1) + nu(2) - nu(2) hot band. The spectrum spans 90 cm(-1) around 1285 cm(-1) with a sample point spacing of 3 x 10(-4) cm(-1) (9 MHz). We report line positions of 72 lines in the nu(1) fundamental band between P(37) and R(38), and 112 lines in the nu(1) + nu(2) - nu(2) hot band (split into two components with e/f rotationless parity) between P(34) and R(33), with uncertainties in the range of 90-600 kHz. We derive upper state constants of both bands from a fit of the effective ro-vibrational Hamiltonian to the line center positions. For the fundamental band, we observe excellent agreement in the retrieved line positions and upper state constants with those reported in a recent study by AlSaif et al. using a comb-referenced quantum cascade laser [J Quant Spectrosc Radiat Transf, 2018;211:172-178]. We determine the origin of the hot band with precision one order of magnitude better than previous work based on FTIR measurements by Toth [http://mark4sun.jpl.nasa.gov/n2o.html], which is the source of the HITRAN2016 data for these bands. (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

In this study, a Fourier transform spectrometer was used for high-resolution broadband measurements of nitrous oxide, retrieving line center frequencies and upper state constants. The results showed excellent agreement with a recent study by AlSaif et al. using a comb-referenced quantum cascade laser. The origin of the hot band was determined with precision one order of magnitude better than previous work.