The anomalous temperature dependence of the sound velocity in water

The quantum yields of naphthalene vapour fluorescence at 225°c and of phenanthrene vapour fluorescence at 365°c excited by the Hg 313 μ line are independent of concentration up to 0·014 and 0·007 moles/l. respectively; this is attributed to fast dissociation relaxation of the excimer at these temperatures.

The fluorescence of naphthacene vapour excited at temperatures of 355–435°c by the group of Hg lines at 365 μ decreases with increasing pressure at pressures below that at which absorption of the incident radiation is virtually complete, and is attributed to a combination of self-quenching and reabsorption of fluorescence. An analysis of the data for the limiting cases of complete and negligible fluorescence reabsorption provides upper and lower limits for self-quenching constant which are consistent with unit collisional quenching efficiency and a lifetime of 5·3 ± 2·2 + 10^-9 sec at 355°c.