Knowledge Bank

The visible absorption spectra of the 4-R-1, 2, 4-triazoline-3, 5-diones (R = methyl, ethyl, or n-butyl) have been measured under moderate resolution. The absorption system is found to extend from 5750 {\AA} to 4950 {\AA} and the predominant features show an approximate vibrational spacing of $591cm-1$ and $380cm-1$, in all cases. A complete radiative lifetime spectrum $(\top RAD$ vs. $\lambda EXCITATION)$ has also been measured for the methyl substituted compound, and the lifetimes are found to range from 55 to 120 nsec. There is obvious structure in this lifetime spectrum, with maxima of matching maxima of absorbance. The effect of added gas has also been investigated for the methyl substituted as well as the ethyl and n-butyl substituted compounds. For the methyl substituted, it is found that upon addition of 50 torr of Ar gas, all states excited fluoresce with the same radiative lifetime. Somewhat similar effects are observed for the other compounds. Conjecture is made concerning the possibility of two $n-\Pi \ast$ transitions in this region, in relation to the time resolved fluorescence work and the absorption spectra.