Atomic, Molecular and Optical Physics

Welcome to the Atomic, Molecular and Optical Physics Group, where research covers many areas of current focus in the AMO community. They can be broadly grouped into:

Atomic and Molecular Spectroscopy (N. Berrah, R. Cote, G. Gibson, P. Gould, V. Kharchenko, D. McCarron, W. Smith, C. Trallero):

  • Theory: We compute photoassociation spectra, analyze experimental spectra and compare them to adjust interaction potentials accurately reproducing measured features. We compute lifetime of molecular states, and how spectral features are affected by the environment (e.g., line shift and broadening, Stark shift of Rydberg states, E2 excitation to high Rydberg levels, etc.).
  • Experiment:
  • We carry out ultrafast experiments with femtosecond and attosecond pulses using either table top lasers at UConn (in three different labs ; Berrah, Gibson, Trallero) and using XUV, VUV and X-ray Free Electron Lasers (FELs) in the US, Japan and Europe. We investigate and measure, with great details, molecular dynamics, occurring in ultrafast timescale.  Our goal is to make a “Molecular Movie” by measuring, as a function of time, all of the physical and chemical processes that are at play, subsequent to photo-induced excitation and ionization of various systems. The different lasers we use allow us to probe valence and inner-shell electrons in matter (atoms, molecules, nanosystems, liquids, solids). Attosecond lasers allow us to probe and aim to understand electronic dynamics while femtosecond laser allow us to probe and aim to understand nuclear dynamics in the systems we study.  Our research has crucial impact to other fields of science such as nanophysics, chemistry and biology.
  • We produces ultracold Rydberg atomic samples and ultracold molecule gases and probe their properties via their spectra. For example, we detected the van de Waals blockade mechanism in ultracold Rydberg gases by studying strong saturation of excitation of specific atomic lines. The strong Rydberg-Rydberg interaction also lead to molecular resonances between Rydberg states that were detected and analyzed; these could allow for the formation of macrodimers, i.e. micron size molecules made of two Rydberg atoms. We also investigate in detail the spectra of Rb2 and KRb in both ground and excited electronic states, to construct precise molecular potentials from which we can find the best path to produce ultracold molecules in their ground ro-vibrational state.

Quantum Optics (R. Cote, N. Dutta, P. Gould, J. Javanainen, C. Roychoudhuri, W. Smith, S. Yelin):

  • Theory: Interference effects in ultracold atom-molecule samples, in electromagnetically- induced-transparency (EIT), many-body effects in cold samples (e.g., super-radiance in Rydberg gases, Bose-Einstein condensates in optical lattices, etc.), and meta-materials (e.g., with negative index of refraction).

Ultracold Atoms and Molecules (R. Cote, P. Gould, J. Javanainen, D. McCarron, S. Yelin):

  • Theory: We study the interaction of atoms with atoms or molecules and their scattering properties (e.g., their scattering lengths or their inelastic collisions), ultracold atoms in optical lattices (e.g., the superfluid-Mott insulator transition in bosonic samples), non-linear effects (e.g., in slow-light and EIT processes), the formation of ultracold molecules (e.g., using photoassociation near Feshbach resonances).
  • Experiment: We probe ultracold atomic samples of Rb atoms to control their scattering properties, and to for ultracold molecules (Rb2 and KRb). We investigate ultracold molecules by obtaining precise spectra that reveal their inner structure. We also study their interaction with external field and among themselves. These will lead to exploring degenerate molecular gases.

Ultrafast laser science (N. Berrah, G. Gibson, C. Trallero):

  • Quantum dynamics: We make use of femtosecond (10-15s) laser and attosecond pulses to study the structure and dynamics of molecules, atoms and solids using table-top lasers or accelerator based-lasers such as Free Electron Lasers (FELs) in the US and abroad. These studies are done by following the formation of atomic or molecular ions and electrons using sophisticated detectors such as Cold Target Recoil Ion Momentum Spectrometer (COLTRIMS) and a Velocity Map Imaging (VMI). These techniques allow us to measure electrons and ions in coincidences with each other, enabling detail information. We also perform similar studies by looking at the extreme non-linear response of the atoms, molecules and media. By using short pulses of light we can track in “real time” how quantum systems evolve after a sudden interaction
  • Optics development: We are interested in developing new optical approaches and methods in ultrafast optics ranging from extreme ultraviolet (XUV) to the infrared. In particular we have interest in the generation and control of few-cycle pulses in the infrared, ranging from 800 nm to 8000 nm and the generation and control of XUV pulses. These XUV pulses have attoseconds (10-18s) in duration and represent the shortest time events to be measured to date. We are currently working in going even beyond the attosecond barrier.

Ion-atom collisions (R. Cote, W. Smith):

  • Experiment: The group of Winthrop Smith uses a hybrid trap to study ion-atom interactions at cold and ultracold temperatures. A hybrid trap, a device first proposed by Prof. Smith, combines a magneto-optic trap (MOT) for neutrals and an r.f. Paul trap for ions in the same volume. We measure collision rates and reactions between cold atoms and ions, the nonlinear dynamics of ion loading and decay from a linear Paul ion trap, and  he sympathetic cooling of atomic and molecular ions with ultracold atoms. We collaborate with Robin Côté, John Montgomery and Harvey Michels (UConn), Reinhold Blümel (Wesleyan University), Douglas Goodman (Wentworth Institute of Technology), and Frank Narducci (Naval Air Systems).
  • Theory: Robin Côté’s group calculates molecular-ion ground and excited-state potential curves and techniques for creating ground state molecular ions in hybrid traps. Starting from these calculations, one can obtain elastic scattering and reaction rates for cold and ultracold ion-atom collisions. Some of these are important for the physics of the solar system and the interstellar medium. We collaborate with Dr. Smith’s group at UConn and other groups around the world.