The widths and positions of several lines in the fluorescence spectrum of ruby with 0.94 at.% Cr3+belonging to the second (N1) and the fourth (N2) nearest neighbor pair systems have been measured between 20° and 270°K. The linewidths are explained in terms of microscopic strains, Raman scattering of phonons, and direct phonon processes. The lineshifts with temperature are due to the absorption and emission of virtual phonons, and are approximately the same for all the lines investigated. A Debye model of phonons was used with different effective Debye temperatures for linewidth and lineshift processes.