Direct Observation of Electronic Intramolecular Energy Transfer through a Large Energy Gap

A double-resonance technique is used to make the first direct observation of collision-induced electronic energy transfer in a diatomic molecule through an energy gap much greater than $\mathrm{kT}$ (208 ${\mathrm{cm}}^{-1\mathrm{}}$ at $T=300\mathrm{}$ K). Surprisingly, $J$ specificity is observable in this transfer process which appears to follow optical-like propensity rules in spite of the large energy gap of ∼ 1760 ${\mathrm{cm}}^{-1\mathrm{}}$ between the initially populated ${\mathrm{N}}_2^{+}$ $A(v^{\prime }=4)$ state and the lower-lying $X(v^{\prime \prime }=7)$ ground-state level to which it is quenched. Room-temperature helium is the collision partner.