Knowledge Bank

Resonant microwave coherence transfer between two levels pairs ($a-a\prime$) and ($b-b\prime$) of two molecular species A and B has been observed. A and B are either different molecules or the same molecule in states uncoupled by collision induced transitions. The frequencies of the two transitions $a\to a\prime$ and $b\to b\prime$ are nearly equal and can be transiently brought in coincidence by applying a suitable Stark field. The coherence transferred from A-molecules to the B-molecules is detected by the techniques of time resolved spectroscopy. The observed phenomena may be interpreted either by collision induced effects between collision partner molecules or by collective effects. The contribution of these two effects are roughly estimated.