High sensitivity CW-Cavity Ring Down Spectroscopy of N 2O near 1.28 μm

Abstract

The absorption spectrum of nitrous oxide, N 2O, in normal isotopic abundance has been recorded by CW-Cavity Ring Down Spectroscopy between 7647 and 7918 cm −1. The spectra were obtained at Doppler limited resolution by using a CW-CRDS spectrometer based on a series of fibered DFB lasers. The typical noise equivalent absorption on the order of α min ≈ 1 × 10 −10 cm −1, allowed for the detection of lines with intensity as weak as 2 × 10 −29 cm/molecule. The positions of 2272 lines of five isotopologues ( 14N 2 16O, 15N 14N 16O, 14N 15N 16O, 14N 2 18O and 14N 2 17O), were measured with a typical accuracy of 1.0 × 10 −3 cm −1. The transitions were rovibrationally assigned on the basis of the global effective Hamiltonian models respective to each isotopologue. The band by band analysis allowed for the determination of the rovibrational parameters of a total of 30 bands, 19 of them being newly reported while new rotational transitions are measured for the others. The maximum deviation of the predictions of the effective Hamiltonian models is 0.18 cm −1 for the line positions of the main isotopologue and up to 1.3 cm −1 for the 14N 2 18O species. Local rovibrational perturbations were evidenced for three bands of 14N 2 16O and the ν 1 + 3 ν 3 band of 14N 2 17O. The interaction mechanisms and the perturbers were univocally assigned on the basis of the effective Hamiltonian models.