Nuclear Spins and Band Spectra of the Selenium Isotopes

An investigation of the rotational structure of the ${{}_{}{}^1{}_{}{}^{}\Sigma _u^{}{}_{}{}^{}}^{+}-{{}_{}{}^1{}_{}{}^{}\Sigma _g^{}{}_{}{}^{}}^{+}$ band system of ${\mathrm{Se}}_2$ in the region 3700-3815A, using separated isotopes of selenium, has made possible the assignment of $I=\frac{1}{2}$ to the nucleus ${\mathrm{Se}}^{77}$, and the confirmation of $I=0\mathrm{}$ for ${\mathrm{Se}}^{78}$ and ${\mathrm{Se}}^{80}$. At the same time a number of new facts regarding the predissociation and the rotational constants of the ${\mathrm{Se}}_2$ molecules are established.