Microwave optical double resonance used as an assignment tool in optical spectroscopy

Abstract

Microwave transitions between excited rovibronic states were used to assign transitions in the optical spectrum of NH 2 using microwave optical double-resonance spectroscopy. The microwave frequency was set so as to pump one particular hyperfine component of the previously observed 1 10, J = 1 2 , Π(0, 10, 0), A ̃ 2A 1 ↔ u , F 2 transition around 6.3 GHz, the frequency of the dye laser was then tuned over a wide spectral range. Double-resonance signals occurred in four level systems whenever the optically excited level was collisionally coupled to either of the microwave pumped levels. This method, when used in conjunction with the results of a conventional absorption spectrum of the molecule, yields information on perturbing states around the Π(0, 10, 0) region. In addition it has proved possible to detect further levels of similar vibronic character to the u state, in particular the spin rotation partners of u and u′. Some discussion on a possible vibronic assignment for these levels is included.