Knowledge Bank

Six absorption bands of $He2$ have been observed in the $600-611\backslash AA$ range. Individual bands exhibit diffuse rotational structure when the absorption cell is cooled with liquid nitrogen. They form a $v\prime$-progression. Attribution is to the transition $\Lambda 1\Sigma u+\leftarrow X1\Sigma g+$ of $He2$. Rotational constants, $Bv\ast \ast \ast$ for the upper state are calculated. The dissociation energy and the term value of the upper state are estimated. A minimum height for the potential ``hump'' in the A-state is determined to be 0.059eV. There is a very close connection between emission and absorption bands of $He2$ around $600\backslash AA$ and also to well known He-continuum with intensity peak near $800\backslash AA$.