Exploring the vibrational series of pure trilobite Rydberg molecules

In trilobite Rydberg molecules, an atom in the ground state is bound by electron-atom scattering to a Rydberg electron that is in a superposition of high angular momentum states. This results in a homonuclear molecule with a permanent electric dipole moment in the kilo-debye range. Trilobite molecules have previously been observed only with admixtures of low- l states. Here we report on the observation of two vibrational series of pure trilobite Rubidium-Rydberg molecules that are nearly equidistant. They are produced by three-photon photoassociation and lie energetically more than 15 GHz below the atomic 22F state of rubidium. We show that these states can be used to measure the electron-atom scattering length at low energies in order to benchmark current theoretical calculations. In addition to measuring their kilo-Debye dipole moments, we also show that the molecular lifetime is increased compared to the 22F state due to the high- l character. The observation of an equidistant series of vibrational states opens the way to observe coherent molecular wave packet dynamics. In trilobite Rydberg molecules a ground state atom is coupled to a Rydberg (high-angular momentum) atom, and a potential well is formed in their potential energy curves. Here the authors report observation of vibrational series in pure trilobite rubidium Rydberg molecules created by three-photon photoassociation.