• Emulating optical cycling centers in polyatomic molecules

      Li, M; Kłos, J; Petrov, A; Kotochigova, S; Li, Ming|0000-0003-0827-5976 (2019-12-01)
      © 2019, The Author(s). An optical cycling center (OCC) is a recently coined term to indicate two electronic states within a complex quantum object that can repeatedly experience optical laser excitation and spontaneous decay, while being well isolated from its environment. Here we present a quantitative understanding of electronic, vibrational, and rotational excitations of the polyatomic SrOH molecule, which possesses a localized OCC near its Sr atom. In particular, we describe the vibrationally dependent trends in the Franck–Condon factors of the bending and stretching modes of the molecular electronic states coupled in the optical transition. These simulations required us to perform electronic structure calculations of the multi-dimensional potential energy surfaces of both ground and excited states, the determination of vibrational and bending modes, and corresponding Franck–Condon factors. We also discuss the extent to which the optical cycling center has diagonal Franck–Condon factors.
    • Fractal universality in near-threshold magnetic lanthanide dimers

      Makrides, C; Li, M; Tiesinga, E; Kotochigova, S; Li, Ming|0000-0003-0827-5976 (2018-02-01)
      The Authors Copyright © 2018. Ergodic quantum systems are often quite alike, whereas nonergodic, fractal systems are unique and display characteristic properties. We explore one of these fractal systems, weakly bound dysprosium lanthanide molecules, in an external magnetic field. As recently shown, colliding ultracold magnetic dysprosium atoms display a soft chaotic behavior with a small degree of disorder. We broaden this classification by investigating the generalized inverse participation ratio and fractal dimensions for large sets of molecular wave functions. Our exact close-coupling simulations reveal a dynamic phase transition from partially localized States to totally delocalized States and universality in its distribution by increasing the magnetic field strength to only a hundred Gauss (or 10 mT). Finally, we prove the existence of nonergodic delocalized phase in the system and explain the violation of ergodicity by strong coupling between near-threshold molecular States and the nearby continuum.
    • Laser controlled charge-transfer reaction at low temperatures

      Petrov, A; Makrides, C; Kotochigova, S (2017-02-28)
      © 2017 Author(s). We study the low-temperature charge transfer reaction between a neutral atom and an ion under the influence of near-resonant laser light. By setting up a multi-channel model with field-dressed states, we demonstrate that the reaction rate coefficient can be enhanced by several orders of magnitude with laser intensities of 106 W/cm2 or larger. In addition, depending on laser frequency, one can induce a significant enhancement or suppression of the charge-exchange rate coefficient. For our intensities, multi-photon processes are not important.