The components of the sharply resolved ultraviolet band of , where peak wave lengths can be determined to ±20 cm−1, do not show any appreciable shift with concentration of activator or flux, or with temperature. The band is quenched at about 190°K and is replaced by a broad featureless band which increases in intensity up to about 570°K and then decreases. The excitation spectra of show two peaks (at 2250 and 3470 Å) which show small shifts with temperatures (50 to 75 Å from − 193°C to room temperature) and a large change of relative intensity (3:1 at −193°C and 1:1 at room temperature).