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We present an optical transmission spectrum for WASP-94A b, the firstatmospheric characterisation of this highly-inflated hot Jupiter. The planethas a reported radius of $1.72^{+0.06}_{-0.05}$ R$_{\textrm{Jup}}$, a mass ofonly $0.456^{+0.032}_{-0.036}$ M$_{\textrm{Jup}}$, and an equilibriumtemperature of $1508 \pm 75$ K. We observed the planet transitspectroscopically with the EFOSC2 instrument on the ESO New TechnologyTelescope (NTT) at La Silla, Chile: the first use of NTT/EFOSC2 fortransmission spectroscopy. We achieved an average transit-depth precision of$128$ ppm for bin widths of $\sim200$ Angstrom. This high precision wasachieved in part by linking Gaussian Process hyperparameters across allwavelength bins. The resulting transmission spectrum, spanning a wavelengthrange of $3800 - 7140$ Angstrom, exhibits a sodium absorption with asignificance of $4.9\sigma$, suggesting a relatively cloud-free atmosphere. Thesodium signal may be broadened, with a best fitting width of $78_{-32}^{+67}$Angstrom in contrast to the instrumental resolution of $27.2 \pm 0.2$ Angstrom.We also detect a steep slope in the blue end of the transmission spectrum,indicating the presence of Rayleigh scattering in the atmosphere of WASP-94A b.Retrieval models show evidence for the observed slope to be super-Rayleigh andpotential causes are discussed. Finally, we find narrow absorption cores in theCaII H&K lines of WASP-94A, suggesting the star is enshrouded in gas escapingthe hot Jupiter.

LRG-BEASTS: sodium absorption and Rayleigh scattering in the atmosphere of WASP-94A b using NTT/EFOSC2