Experimental and theoretical study of line shift and mixing in the ν4 band of NH3 perturbed by N2

The shift coefficients and line-mixing parameters of rovibrational–inversion transitions in the ν4 band of ammonia (NH3) perturbed by nitrogen (N2) have been measured at room temperature with a high-resolution Fourier transform spectrometer. The collisional shift and line mixing are obtained from the non-linear least-square multi-pressure fitting techniques. Comparison is made with the results of theoretical calculation based on semi-classical model extended to the case of symmetric top molecule with inversion motion. The shifts and the line-mixing parameters are calculated using, respectively the approach developed by Robert and Bonamy and the state-to-state cross-section. The agreement is satisfactory on the average. Good agreement is also obtained for line mixing with previous measurements.