With the next generation of CMB surveys promising to map linear perturbation modes (in both temperature and E-mode polarization) down to the cosmic variance limit for $\ell$ below $\sim 3000$, cosmologists are turning to different avenues to further constrain the $\Lambda CDM$ model. Primordial gravitational waves, in the form of linear B-modes polarization, could be detected in the near future by upcoming ground-based experiments. Secondary anisotropies are another more recently studied potential source of cosmological information. CMB lensing for example, has been successfully measured and used to obtain stringent constraints on neutrino masses. The Sunayev – Zel’dovich (SZ) Effects, both kinetic and thermal, although they heavily depend on astrophysical processes, carry their own cosmological information.
Among these secondaries, Rayleigh scattering of the CMB is a less studied yet potentially powerful probe of the recombination history. Scattering of CMB photons off neutral species right after recombination presents a distinctive $\nu^4$ scaling with frequency as well as a strong correlation with the primary CMB. These unique features should guarantee its detection by the next generation of ground based CMB experiments. We will present detectability forecasts combining the Simons Observatory and CCAT-prime telescopes as well as more futuristic space missions. Finally, we will present potential cosmological implications of the detection of this signal by studying improvement of parameter constraints.