In most ions and molecules the atoms occupy equilibrium positions. There are indications that there are other ones which do not have a stable structure, also not in time-average and may be not at temperatures of 1 K. One example seems to be CH_5⁺, a fascinating highly fluxional cation. This and similar molecules are fundamentally interesting because they violate the "rules" of chemical bonding (carbon is only supposed to make four bonds, not five).

Since the 1960s, when petrochemical experiments suggested the existence of CH_5⁺, scientists have been trying to record a complete spectrum of it, but the molecule won't sit still. Some progress was made recently, using our low-temperature ion trap; however, it seems to be that the temperature of 100 K was still too high. Presently we are working on methods, to cool molecular ions in a trap down to 1 K.

There are many more molecules with interesting structures, e.g. hydrogen or carbon clusters. Deuterated molecules play a central role in the understanding of interstellar chemistry. Replacement of H vs. D raises - at very low temperatures and in weakly bound molecules such as H_3⁺ - H - whether on can see signatures of Bose-chemistry.