Pumping mechanism of Javan’s pure rotational OH laser

Javan and coworkers have reported pure rotational laser oscillation from OH and OD in a pulsed discharge through H2‐O2‐SF6 mixtures. The pumping mechanism was not established, but it was thought at the time to be chemical. The intensity distribution can be understood as resulting from the electronic to rotational transfer of 13 200 cm−1 from O2(1Σ+g ) to ground vibrational state OH(2Π) leaving the O2 in its ground 3Σ−g state. Unexcited OH would be formed from either the reaction O+H2 = OH+H or H+O2 = OH+O. Nothing can be said about the efficiency of this E‐R transfer compared to E‐V; however, E‐R appears to be a new mechanism for pumping diatomic, pure rotational inversions. The full explanation of this laser also demands the conclusion that SF6, like the rare gases, can serve as a collision partner inducing intramolecular V‐R transition in OH.