Newsfeeds

Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers

Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics

IOPscience

  • Doppler-free selective reflection spectroscopy of the 6s 2 ...
    Selective reflection (SR) spectroscopy of the 6s 7p electric dipole transition of Caesium ( nm) is performed for the first time using a nanometric-thin cell (L = 50–1500 nm, C). We successfully form narrow resonances corresponding to the hyperfine transitions. All transitions are well spectrally resolved, and the geometry of the cell allows us to obtain a strong 30 times narrowing of the Doppler width with a single beam pass. For lower thicknesses (L < 400 nm), we observe a red shift of the SR lines, which we attribute to atom-surface interactions, and provide estimates of the C3 interaction coefficient. The oscillator strengths of the 6s 7p hyperfine transitions are about two orders of magnitude smaller than that of the Cs D2 line at 852 nm. Our experimental measurements are in good agreement with theoretical calculations. We emphasize the advantage of nanocell spectroscopy compared to the well-known saturated absorption method and present possible applications.

  • Stochastic Schrödinger equation for homodyne measurements of strongly correlated systems
    Starting from an experimentally feasible atomic setup, we derive a stochastic Schrödinger equation that captures the homodyne detection record of a strongly interacting system. Applying the rotating wave approximation to the linear atom-light coupling, we arrive at a reduced equation formulated solely in terms of atomic operators. In the appropriate limit, this equation converges to that of Gaussian continuous quantum measurement—revealing that the complexities of real-world detection can, under certain conditions, echo the elegance of idealized theory. To illustrate the utility of this framework, we numerically study the Bose–Hubbard model under continuous observation, showing that time-domain analysis of the measurement signal uncovers rich dynamical features, including quantum jumps, that are obscured in ensemble-averaged spectral data.

  • Phenomenological rate formulas for over-barrier ionization of hydrogen and helium atoms in strong constant electric fields
    Nonrelativistic over-barrier ionization (OBI) of atoms in strong constant electric fields is studied, focussing on hydrogen and helium as concrete examples. Our goal is, on the one hand, to develop an intuitive physical picture behind established empirical formulas for the ionization rate. We show that the ionization rate in a near OBI regime can be modeled quantitatively by extending corresponding tunneling rates by the combined action of the Stark effect and a widened electron emission angle. On the other hand, we present analytical rate formulas in a far OBI regime which closely agree with available numerical data. In result, compact rate expressions describing OBI of hydrogen-like and helium atoms in a broad range of applied field strengths are obtained. They can be useful, for example, in numerical laser-plasma simulation codes to describe elementary ionization events.

  • High-order above-threshold ionization: improved strong-field approximation vs. numerical solution of the time-dependent Schrödinger equation
    For decades the strong-field approximation (SFA) has been a theoretical backbone for describing the strong-field related phenomena such as above-threshold ionization (ATI) and high-order harmonic generation, even though it is well-known that it cannot accurately account for the long-range Coulomb interaction between the liberated electron and residual atomic ion. In this paper, we theoretically investigate high-order ATI. We use numerical solutions of the time-dependent Schrödinger equation (TDSE) and an improved SFA that includes electron rescattering. The analysis is performed for atomic anions and neutral atoms exposed to elliptically polarized laser fields. To validate the SFA and test its applicability, we compare both theoretical approaches for various targets and laser field parameters. We also show that the improved SFA in which the final electron plane wave is replaced by the Coulomb distorted plane wave leads to a better agreement with the results obtained using the solutions of the TDSE.

  • Collective modes of two-species Bose–Einstein condensates in a Josephson junction barrier
    The ultracold atoms are an ideal platform to implement atomtronics and Josephson junctions analogous to superconducting circuits. The collective modes of a Bose gas split by a potential barrier have been known. However, the role of barriers on the collective excitation spectra of ultracold atomic mixtures has not been examined. Here, we examine the low-lying collective modes of (an)harmonically trapped quasi-one-dimensional Bose–Einstein condensates (BECs) in a Josephson barrier by employing the variational approach and Bogoliubov theory. We first show that the anharmonicity of the external potential leads to an increase in the critical barrier strength of mode softening in a single-species condensate. The Josephson barrier drives the softening of in-phase and out-of-phase dipole modes of two-species BECs, and consequently leads to two additional zero-energy Goldstone modes in the miscible phase, in agreement with the variational approach. Furthermore, the sandwich immiscible state results in an additional Goldstone mode due to the barrier, in contrast to the spatially symmetry-broken side-by-side profile. Our results unveil the distinct collective response of the Josephson barrier in binary mixtures owing to interspecies atomic correlations.