Experimental observation of the ν${}_1$+3ν${}_3$ combination bands of ${}^{16}$O${}^{14}$N${}^{18}$O and ${}^{18}$O${}^{14}$N${}^{18}$O in the near infrared spectral region

The first observation of the ν${}_1$+3ν${}_3$ combination band of the nitrogen dioxide isotopologue ${}^{16}$O${}^{14}$N${}^{18}$O is presented. The band was measured using Fourier-Transform Incoherent Broad-Band Cavity Enhanced Absorption Spectroscopy (FT-IBBCEAS) in the region between 5870 cm${}^{-1}$ and 5940 cm${}^{-1}$. To confirm the assignment, the band was simulated using a standard asymmetric top Watson Hamiltonian using extrapolated rotational and centrifugal distortion constants. Furthermore, the first experimental observation of the ν${}_1$+3ν${}_3$ band of the ${}^{18}$O${}^{14}$N${}^{18}$O isotopologue is also reported. The positions of ro-vibrational lines of the ν${}_1$+3ν${}_3$ band of the naturally most abundant isotopologue ${}^{16}$O${}^{14}$N${}^{16}$O were used for wavenumber calibration of line positions.