Title: Rayleigh-Brillouin light scattering spectroscopy of nitrous oxide (N$_2$O),
Abstract: High signal-to-noise and high-resolution light scattering spectra are
measured for nitrous oxide (N$_2$O) gas at an incident wavelength of 403.00 nm,
at 90$^\circ$ scattering, at room temperature and at gas pressures in the range
$0.5-4$ bar. The resulting Rayleigh-Brillouin light scattering spectra are
compared to a number of models describing in an approximate manner the
collisional dynamics and energy transfer in this gaseous medium of this
polyatomic molecular species. The Tenti-S6 model, based on macroscopic gas
transport coefficients, reproduces the scattering profiles in the entire
pressure range at less than 2\% deviation at a similar level as does the
alternative kinetic Grad's 6-moment model, which is based on the internal
collisional relaxation as a decisive parameter. A hydrodynamic model fails to
reproduce experimental spectra for the low pressures of 0.5-1 bar, but yields
very good agreement ($< 1$\%) in the pressure range $2-4$ bar. While these
three models have a different physical basis the internal molecular relaxation
derived can for all three be described in terms of a bulk viscosity of $\eta_b
\sim (6 \pm 2) \times 10^{-5}$ Pa$\cdot$s. A 'rough-sphere' model, previously
shown to be effective to describe light scattering in SF$_6$ gas, is not found
to be suitable, likely in view of the non-sphericity and asymmetry of the N-N-O
structured linear polyatomic molecule.