THE FORBIDDEN ROTATION AND ROTATION-VIBRATION SPECTRUM OF $H_{2}^{+}$

$^{a}$R.E. Moss, Chem. Phys. Lett. 206, 83(1993), and references therein. $^{b}$Section 17.7 of the book Molecular Symmetry and Spectroscopy. 2nd Edition, by P.R. Bunker and P. Jensen, NRC Research Press, Ottawa 1998. See http//www.nrc.ca/cisti/journals/41653 for the table of contents and ordering information. $^{c}$P.R. Bunker and R.E. Moss, Chem. Phys. Lett. 316, 266 (2000).Author Institution: Steacie Institute for Molecular Sciences, National Research Council of Canada; Department of Chemistry, University of SouthamptonPrevious studies of the g/u electronic symmetry breaking interaction between the rotation-vibration levels of the $X^{2}\Sigma^{+}_{g}$ ground electronic state and the $A ^{2}\Sigma^{+}_{u}$ first excited electronic state of $H_{2}^{+}$ have focused on explaining the large hyperfine structure observed in some rovibronic transitions between these electronic $states^{a,b}$. The interaction is an ortho-para interaction between levels of the two electronic states. It gives rise to an interesting new electric dipole spectrum that consists of forbidden rotation and rotation-vibration transitions within the $X^{2}\Sigma^{+}_{g}$ ground state involving levels that are near the dissociation limit. Such a spectrum will occur for any homonuclear diatomic in having nuclei with non-zero spin such as $^{3}He_{2}^{+}$, $Li^{+}_{2}$ and $^{21}Ne_{2}^{+}$