The work presented in this thesis is primarily experimental but also contains an important theoretical extension to gain further insight into the optical spectroscopy of atomic ns2 metal atoms, mercury and manganese isolated in cryogenic thin films of rare gases argon, krypton and xenon. The luminescence spectroscopy of solid-state M/RG (M = Hg and Mn; RG = Ar, Kr and Xe) samples has been recorded employing both time-integrated (steady-state) and time-resolved methods. The impetus for the selection of the Hg/RG systems being the availability of solid-state spectroscopic and gas phase pair-potentials data that allowed the development of a theoretical model. The theoretical analysis conducted on the Hg/RG systems, yielded a qualitative interpretation of the recorded experimental data, providing information on the vibronic modes leading to the observed luminescence. In contrast, the investigation of Mn/RG solids was motivated by the absorption similarities between this transition metal atom and the simpler Hg/RG system, as both exhibit a ground ns2 electronic configuration and excited states derived from the ns1np1 configuration. However, the existence of low lying excited states in Mn, originating from electronic configurations other than the [Ar]3d54s4p configuration accessed in absorption, provides multiple radiative and non-radiative relaxation channels for excited state populations. The luminescence spectroscopy of Hg and Mn atoms isolated in rare gas matrices has shown that the solid state environment provides an ideal environment to study the solvation of ground and excited state metal atoms. It allows the extraction of information on long-lived electronic transitions (> 100 µsec) that cannot be observed in gas phase experiments. The experimental results obtained for the Mn/RG systems have shown that the site of isolation governs the excited state interactions with the host. This observation therefore would allow the extension of this work to investigate site selective excited state reactions with reagents such as CH4, CH3F, NH3 and H2- doped rare gas matrices.