ee Boe at ae oO POLARIZATION ABSORBANCE (RELATIVE) 18] | 290 i 300 J ] 320 340 j 360 |. 380 j =6400 0 WAVELENGTH (mj) Fic. 139.-—-Absorbance of 1,3,6,8-tetrapheny] pyrene and corresponding polarization of emission tion at the long-wavelength end of the range is that of the grating, 410 mp. SEARCH FOR HIDDEN LEVELS Several additional compounds have been studied; also, some of those studied previously have been re- studied for more complete information. As pointed out previously, in general it has been found not worth while to study a compound in a liquid medium unless the compound has a very short fluorescence decay time of the order of one nanosecond) because otherwise depolarization reduces the values to the point where trends are obscured. Table 66 gives the additional results to date. The long-wavelength edge of the first absorption band is given to provide orien- tation for the reader. Also, to aid in the visualization of the results, curves are given in Figure 139 of absorption and corresponding polarization of emission