Precise study of asymptotic physics with subradiant ultracold molecules

Abstract

Weakly bound molecules have physical properties without atomic analogues, even as the bond length approaches dissociation. In particular, the internal symmetries of homonuclear diatomic molecules result in formation of two-body superradiant and subradiant excited states. While superradiance [1][2][3] has been demonstrated in a variety of systems, subradiance [4][5][6] is more elusive due to the inherently weak interaction with the environment. Here we characterize the properties of deeply subradiant molecular states with intrinsic quality factors exceeding 10 13 via precise optical spectroscopy with the longest molecule-light coherent interaction times to date. We find that two competing effects limit the lifetimes of the subradiant molecules, with different asymptotic behaviors. The first is radiative decay via weak magnetic-dipole and electric-quadrupole interactions. We prove that its rate increases quadratically with the bond length, confirming quantum mechanical predictions. The second is nonradiative decay through weak gyroscopic predissociation, with a rate proportional to the vibrational mode spacing and sensitive to short-range physics. This work bridges the gap between atomic and molecular metrology based on lattice-clock techniques [7], yielding new understanding of long-range interatomic interactions and placing ultracold molecules at the forefront of precision measurements.Simple molecules provide a wealth of opportunities for precision measurements. Their richer internal structure compared to atoms enables experiments that push the boundaries in determinations of the electric dipole moment of the electron [8], the electron-to-proton mass ratio and its variations [9,10], and parity violation [11]. Diatomic molecules are moving to the forefront of manybody science [12] and quantum chemistry [13], providing glimpses into fundamental laws [14]. However, this attractive complexity of molecular structure has historically posed difficulties for manipulation and modeling [15]. This work removes many of these barriers by employing techniques of optical lattice atomic clocks [16,17] to control the quantum states of weakly bound homonuclear diatomic strontium molecules, in particular by using state-insensitive optical lattices [18] for molecular transitions with three types of optical transition moments. We observe strongly forbidden optical transitions in this asymptotic diatomic system, an ideal regime for studying the breakdown of the ubiquitous dipole approximation where the size of the quantum particle is a significant fraction of the resonant wavelength. We explain these observations with a state-of-the-art ab initio molecular model [19] and asymptotic scaling laws. The results prove that the quantum mechanical effect of subradiance can be exploited for precision spectroscopy, and demonstrate the promise of combining precise state control, coherent manipulation, and accurate ab initio calculations with recently available ultracold molecular systems.We create Sr 2 molecules by photoassociation [20] from ...

Electromagnetically induced transparency with superradiant and subradiant states

“…The superradiance and subradiance of two interacting atoms has attracted much interest both theoretically [24,25] and experimentally [26][27][28][29][30]. In this paper, we use superradiance and subradiance to construct EIT and investigate the new feature in the EIT absorption spectrum involving with the cooperative effect and the counterrotating wave terms.…”

Reexamination of the calculation of two-center, two-electron integrals over Slater-type orbitals. III. Case study of the beryllium dimer

“…[3] for the theoretical explanation of the unusual quadratic Zeeman shifts in the Sr 2 molecule, or Ref. [4] for interpretation of the observed subradiant states of Sr 2 . Electronic structure calculations can also be used to predict new schemes for the formation of ultracold diatomic molecules [5][6][7][8][9].…”

Transition moments between excited electronic states from the Hermitian formulation of the coupled cluster quadratic response function

“…Until recently, properties of the excited electronic states were not easily available in high-resolution experiments, but with the advances of new spectroscopic techniques in the hot pipe 4? -7 and ultracold experiments, [8][9][10][11][12] more and more accurate experimental data become available and possibly need theoretical interpretation. Theoretical information about the transition moments between the excited states is also necessary to propose new routes to obtain molecules in the ground rovibrational state (see, e.g., Ref.…”