Knowledge Bank

Full GVB-CI calculations have been carried out on the low-lying doublet states of the nitrogen molecule-ion using the orbitals obtained from the calculations on the ground state of $N2$. The calculated and experimental adiabatic excitation energies for the known states of $N2+$ are given in Table I. [FIGURE] Five new bound doublet electronic states of $N2+$ have been found within 12 eV of the $X2\Sigma g+$ state. $A2-o――g$ state dissociating into $N(2D)+N+(3P)$, has been located 1.3 eV above the $D2\Pi g$ state. Two more $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi g$ states have been found 2.0 and 3.6 eV above the $D2\Pi g$ state. In addition, two $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Delta u$ states are found which lie close in energy and cross the $C2\Sigma u+$ state near the minimum in its potential energy curve. A repulsive $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma u+$ state ``crosses” the $C2\Sigma u+$ state approximately 3 eV above its minimum. States of $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Sigma -$ symmetry have not yet been studied. The anomalous shape of the potential energy curve of the $B2\Sigma u+$ state as observed by $Douglas1$ can be attributed to an avoided crossing of two potential curves, one arising from ionization of a 2s-orbital, the other from ionization of a $2p\sigma$-orbital. Accurate GVB and GVB-CI calculations are now being carried out on selected ion states.