Ultralong-range Rydberg trimer molecules are spectroscopically observed in an ultracold gas of Cs(nd_{3/2}) atoms. The anisotropy of the atomic Rydberg state allows for the formation of angular trimers, whose energies may not be obtained from integer multiples of dimer energies. These nonadditive trimers coexist with Rydberg dimers. The existence of such effective three-body interactions is confirmed with the observation of asymmetric line profiles and interpreted by a theoretical approach that includes relativistic spin interactions. Simulations of the observed spectra with and without angular trimer lines lend convincing support to the existence of effective three-body interactions.
Ultralong-range Rydberg trimer molecules are spectroscopically observed in an ultracold gas of Cs(nd_{3/2}) atoms. The anisotropy of the atomic Rydberg state allows for the formation of angular trimers, whose energies may not be obtained from integer multiples of dimer energies. These nonadditive trimers coexist with Rydberg dimers. The existence of such effective three-body interactions is confirmed with the observation of asymmetric line profiles and interpreted by a theoretical approach that includes relativistic spin interactions. Simulations of the observed spectra with and without angular trimer lines lend convincing support to the existence of effective three-body interactions.
Ultralong-range Cs 2 Rydberg-ground molecules ( nD 5/2 + 6 S 1/2 F ) (33 ≤ n ≤ 39, F = 3 or 4) are investigated by a two-photon photo-association spectroscopy of an ultracold Cs gas. Two vibrational ground molecular spectra of triplet 3 Σ and hyperfine mixed singlet-triplet 1,3 Σ molecular states and their corresponding binding energies are attained. The experimental observations are simulated by an effective Hamiltonian including low energy electron scattering pseudopotentials, the spin-orbit interaction of the Rydberg atom, and the hyperfine interaction of the ground-state atom. The zero-energy singlet and triplet s-wave scattering lengths are extracted by comparing the experimental observations and calculations. Dependences of the measured binding energies on the effective principal quantum number, n eff = n − δ D ( δ D is the quantum defect of Rydberg D state), yield the scaling of n eff − 5.60 ± 0.16 ( 3 Σ , F = 3 ) , n eff − 5.62 ± 0.16 ( 3 Σ , F = 4 ) for deep triplet potential and n eff − 5.65 ± 0.38 ( 1 , 3 Σ , F = 3 ) , n eff − 6.19 ± 0.14 ( 1 , 3 Σ , F = 4 ) for shallow mixed singlet-triplet potential well. The simulations of low-energy Rydberg electron scattering show agreement well with the experimental measurements.
In this thesis, we investigate few-body physics and many-body physics of ultralong-range Rydberg molecules. Ultralong-range Rydberg molecules are formed through scattering processes between Rydberg electrons and ground state atoms. The huge size of the Rydberg electron's orbit makes the Rydberg electron able to interact with more than one ground state atom in cold atomic gases with atom number densities from 1012 cm−3 to 1014 cm−3. In cold atomic gases, the ground state atoms on average are far away from each other. They are weakly interacting. Depending on the angular momentum state of the Rydberg electron, two types of polyatomic Rydberg molecules have been studied. When the Rydberg electron is in an ns state, the isotropic probability distribution of the Rydberg electron makes the Rydberg electron interact with different ground state atoms equally. The total binding energy is a summation of the binding energy from each scattering process. These additive interactions have been studied using Cs 6s+83s and 6s+90s polyatomic Rydberg molecules in this thesis. When the Rydberg electron is in an l>0 angular momentum state, spatial correlations between different ground state atoms are established through the anisotropic probability distribution of the Rydberg electron. The total binding energy depends on the relative positions of different ground state atoms. These nonadditive interactions are studied using Cs 6s+6s+34d and 6s+6s+36d triatomic Rydberg molecules in this thesis.
We calculate vibrational spectra of ultralong-range Cs(32p) Rydberg molecules which form in an ultracold gas of Cs atoms. We account for the partial-wave scattering of the Rydberg electrons from the ground Cs perturber atoms by including the full set of spin-resolved 1,3SJ and 1,3PJ scattering phase shifts, and allow for the mixing of singlet (S=0) and triplet (S=1) spin states through Rydberg electron spin-orbit and ground electron hyperfine interactions. Excellent agreement with observed data in Saßmannshausen et al. [Phys. Rev. Lett. 113, 133201(2015)] in line positions and profiles is obtained. We also determine the spin-dependent permanent electric dipole moments for these molecules. This is the first such calculation of ultralong-range Rydberg molecules in which all of the relativistic contributions are accounted for.
Abstract Rydberg molecules are an essential ingredient of cold molecular sciences. Due to the richness of interactions between Rydberg atoms and neutral atoms, new kinds of Rydberg molecules and binding mechanisms are still to be discovered. In this work, we predict the existence of long-range van der Waals trimers in dilute atom-gas mixtures. These are bound states of a Rydberg atom and a diatomic polar molecule mediated by the long-range van der Waals interaction. This binding mechanism gives rise to trimers with sizes between 5 and 500 nm and binding energies between 0.2 kHz and 2 MHz depending on the atomic principal quantum number n and orbital angular momentum L. We show that these trimers can be produced via two-photon photoassociation, with rates on the order of (10−13 - 10−11) cm3s−1 for temperatures in the range of (0.5 μ K - 10 μ K), and discuss the feasibility of observing trimer resonances.
We measure nonlocal third-order spatial correlations in nondegenerate ultracold gases of bosonic (84Sr) and spin-polarized fermionic (87Sr) strontium through studies of the formation rates for ultralong-range trimer Rydberg molecules. The trimer production rate is observed to be very sensitive to the effects of quantum statistics with a strong enhancement of up to a factor of 6 (3!), in the case of bosonic 84Sr due to bunching and a marked reduction for spin-polarized fermionic 87Sr due to antibunching. The experimental results are compared to theoretical predictions and good agreement is observed. The present approach opens the way to in situ studies of higher-order nonlocal spatial correlations in a wide array of ultracold atomic-gas systems.
Rydberg molecules, Rydberg-atom or Rydberg-molecule, are an essential ingredient of cold molecular sciences. However, due to the richness of Rydberg-neutral interactions, new kinds of Rydberg molecules and binding mechanisms are still to be discovered. In this work, we predict the existence of ultra-long-range van der Waals trimers in dilute atom-gas mixtures. These are bound states of a Rydberg atom and a diatomic polar molecule mediated by the long-range van der Waals interaction. This new binding mechanism gives rise to trimers with sizes between 5-500~nm and binding energies between 2 MHz and 0.2 kHz depending on the atomic principal quantum number n and orbital angular momentum L. We show that these molecules can be produced via two-photon photoassociation, with rates on the order of (10−13 - 10−11) cm3s−1 for temperatures in the range of (0.5 μK - 10μK), and discuss the feasibility of observing trimer resonances.