Precision frequency comb spectroscopy of the ${}^{14}$N${}_2$O, ${}^{14}$N${}^{15}$NO, ${}^{15}$N${}^{14}$NO, and ${}^{15}$N${}_2$O isotopocules in the 3300-3550 cm${}^{-1}$ range

Abstract

Nitrous oxide is a long-lived greenhouse gas. Its isotopic composition provides valuable insights into sources and sinks, and about the mechanism of formation. A major challenge in the spectroscopic analysis of the isotopocule compositions is the availability of accurate spectroscopic parameters, particularly for the minor ${}^{15}$N isotopocules. In this work, we introduce high-resolution spectroscopic measurements of four isotopocules of nitrous oxide: ${}^{14}$N${}_2$O, ${}^{14}$N${}^{15}$NO, ${}^{15}$N${}^{14}$NO, and ${}^{15}$N${}_2$O in the mid-infrared range of 3300 - 3550 cm${}^{-1}$, using a frequency comb-based Fourier transform spectrometer. The nitrous oxide samples were obtained from a chemical synthesis involving acid-catalyzed amine-borane reduction of equimolar amounts of ${}^{15}$N isotopically enriched sodium nitrite and ${}^{14}$N sodium nitrite. The high-resolution spectra, measured in a temperature-controlled single-pass absorption cell, were used to retrieve line center frequencies and relative intensities for a total of 426 rovibrational transitions of the $\nu$${}_1$ + $\nu$${}_3$ band of the four isotopocules, and of the one order of magnitude weaker 2$\nu$${}_2$ + $\nu$${}_3$ and $\nu$${}_1$ + $\nu$${}_2$ + $\nu$${}_3$ - $\nu$${}_2$ bands in the same spectral region. We compare the determined line center frequencies and relative intensities with spectroscopic parameters available in high-resolution molecular databases. For ${}^{14}$N${}_2$O, ${}^{14}$N${}^{15}$NO and ${}^{15}$N${}^{14}$NO we find good agreement with the HITRAN database. The ${}^{15}$N${}_2$O isotopocule is missing in HITRAN, and we find that its line center frequencies in the GEISA database, the Institute of Atmospheric Optics database, as well as the Ames-1 line list deviate severely from the comb measurements.

References in corpus (4)

• ExoMol line lists -- LIX. High-temperature line list for N${}_2$O
• Precision Spectroscopy of Nitrous Oxide Isotopocules with a Cross-Dispersed Spectrometer and Mid-Infrared Frequency Comb
• Isotope Ratio Dual-Comb Spectrometer
• Line positions and intensities of the ${\nu }_1$ band of ${}^{12}$CH${}_3$I using mid-infrared optical frequency comb Fourier transform spectroscopy

Cited by in corpus (2)

• Combined frequency comb and continuous wave cavity-enhanced optical-optical double-resonance spectrometer in the 1.7 $\mu$m range
• Formation of HNC and HCN isomers in molecular plasmas revealed by frequency comb and quantum cascade laser spectroscopy