The Magnetic Rotation Spectrum and Heat of Dissociation of the Lithium Molecule

Abstract

The magnetic rotation spectrum of the green, $^{1}\ensuremath{\Pi}\ensuremath{-}^{1}\ensuremath{\Sigma}$, band system of ${\mathrm{Li}}_{2}$ has been observed and used to locate bands with high quantum numbers and so to obtain an accurate value for the heat of dissociation of the normal ${\mathrm{Li}}_{2}$ molecule, yielding ${{D}_{0}}^{\ensuremath{'}\ensuremath{'}}=1.14\ifmmode\pm\else\textpm\fi{}0.03$ volts. The spectrum is less simple than in ${\mathrm{Na}}_{2}$, for instance, in that we observe not only a strong line at the head of each band, but also a few lines of the $P$ and $R$, but not $Q$, branches. An improved method of plotting Franck-Condon diagrams is illustrated.