Knowledge Bank

In a $previous1$ experiment on the collisional deactivation of electronically excited $N2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$, it was assumed that collision induced electronic energy transfer occurs rapidly between the initial, laser populated $A2\Pi u(v\prime =4)$ level and its adjacent ground state, $v\prime \prime =8$ level. In the present work, a two laser, optical-optical double resonance technique is used to probe the rotational manifolds of these vibrational levels for the A and X states to show directly and conclusively that rapid electronic energy transfer occurs between these two levels. Because $N2\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ is homonuclear, its Hamiltonian has no perturbing terms that connect the $A2\Pi u$ and $X2\Sigma g+$ states. Hence, energy transfer between the rotational manifolds of these two different electronic states cannot occur through ``gates'' of perturbed rotational levels formed in the free molecule. Rotational selection rules deduced from this work will be discussed.