Major processes of alkali aerosol plasma formation in a high-temperature gas flow during injection and subsequent fragmentation of a liquid-metal jet are considered. Spatial distribution of spectral absorption coefficients is determined at frequencies of both resonant and subsidiary lines of an alkali spectrum. An algorithm is described for calculating the radiation transfer with account for light reflection from a droplet surface under conditions of strong spatial inhomogeneity of optical plasma characteristics around intensively evaporating alkali metal droplets. On the basis of given calculated spectral line profiles, am optical diagnostic for determining parameters of the 'liquid-metal nucleus +vapor shell' system is proposed.