The interaction of thermal energy from the environment with motional degrees of freedom is well known and often referred to as Brownian motion (also thermal motion). But in the case of polar molecules,the internal degrees of freedom - in specific the rotational quantum state - are also influenced by the thermal radiation. So far, the detection of the rotational state was only possible by destroying the molecule. However, and a German research group has now demonstrated the first implementation of a non-destructive state detection technique for molecular ions.
Source: phys.org