Knowledge Bank

The ultraviolet absorption spectra of isobutene and isobutene-$d8$ have been measured between 1800 and 1300 {\AA}. (From the blue of the main - $\Pi \to \Pi \ast$ system to the first ionization.) To the blue of the relatively sharp, structured band at $\sim 1488$ {\AA} $(67 173cm-1)$the spectrum is composed of structured Rydberg bands. Most of these are members of a d-Rydberg series $(\delta \sim 0.12)$. Between the $\sim$ 1488 {\AA} band and the 1790 {\AA} band previously $analyzed1$ there are several diffuse transitions. The relative intensities of these transitions differ in the -$h8$ and -$d8$ substituted molecules. Probable assignments for these transitions will be discussed.