Rayleigh spectra of N₂ fluid

Abstract

The normalized second moments of rotational Rayleigh bands of fluid N₂ are reported versus density at various temperatures (296, 202 and 150 K). The reduced second moments fit quite well a universal curve which differs significantly from the pure rotational value in the overall density range investigated (50 < ρ < 700 amagat). The discrepancies are attributed to the induced contributions. In particular, the purely collision induced contributions are responsible for the low density decay, while the cross interference between permanent and induced anisotropy increases the second moment at increasing density. A ‘theoretically’ constructed second moment is reported which reproduces quite well the experimental data up to the critical density. Experimental torques derived from M ₄/M ₂ and M ₄/Mo have been briefly discussed. Some conclusions on the spectral shape analysis and mean square torque values have been worked out.