N_2O weak lines observed between 3900 and 4050 cm^-1 from long path   absorption spectra
  Previously unobserved nitrous oxide transitions around 2.5 $\mu$m are measured by intracavity laser absorption spectroscopy (ICLAS) analyzed by time-resolved Fourier transform (TRFT) spectrometer. With an accuracy of the order of 10^-3 cm^-1, measured positions of 1637 assigned weak transitions are provided. They belong to 42 vibrational transitions, among which 33 are observed for the first time. These data are believed to be useful in particular to monitoring atmosphere purposes. 
Herv\'e Herbin (PPM), Nathalie Picqu\'e (PPM), Guy Guelachvili (PPM),   Evgeni Sorokin (TU WIEN), Irina T. Sorokina (TU WIEN)