Rydberg molecules are like a pair of dancers holding hands at arm's length. One partner is an ion, the other is an atom, and the bond between them is as weak as an invisible thread. Such a pair can exist for only an instant, but that instant stretches into microseconds — an eternity by the standards of the microworld.
Scientists have calculated how quickly such molecules, made of rubidium and lithium, fall apart. It turns out that the decay rate doesn't change smoothly but in jumps, depending on the quantum number n. This is like a pendulum swinging now stronger, now weaker in time with external pushes. The reason is quantum interference: probability waves alternately amplify and cancel each other out.
Such calculations will help experimentalists observe molecular decay in real time using an ion microscope. It's like filming a sandcastle as it crumbles — except instead of sand, you have quantum waves.
as written by the authors arXiv:2608.12716v1
We investigate predissociation in homonuclear ($$^{87}$$Rb$$^*$$$$^{87}$$Rb$$^+$$) and heteronuclear ($$^{87}$$Rb$$^*$$$$^{7}$$Li$$^+$$) long-range Rydberg atom-ion molecules. Owing to their micron-scale bond lengths, these dissociate on time scales far removed from those of more tightly bound diatomic molecules. We employ the eigenchannel $$R$$-matrix method to compute predissociation rates for a broad range of principal quantum numbers $$n$$. The rates depend strongly on the mass, but more remarkably display a rapid and periodic variation as a function of $$n$$ as well as within a single vibrational ladder. A semiclassical Landau-Zener-St\"uckelberg analysis reveals that St\"uckelberg interference governs the decay process and produces the observed variation in the molecular lifetime. Although the heavy mass of the homonuclear Rb molecule constrains its predissociation rates to a sub-kHz level, the lighter molecule $$^{87}$$Rb$$^*$$$$^{7}$$Li$$^+$$ dissociates on time scales competitive with radiative and collisional decay. This can enable in situ study of non-adiabatic decay via ion microscopy.
Rydberg molecules were predicted back in 2000, but were first created in the lab only in 2016.