Abstract
The R‐line fluorescence in ruby was excited with the nanosecond light pulses, and the slope of the rise curve was studied as a function of the pulse width at room temperature. The purpose of the experiment was to determine the value or the upper limit of the nonradiative relaxation time between the pump bands 4T1, 2 and the fluorescence state 2E. The upper limit of 5 nsec was determined. A brief review of previous work is given.