In a standing wave of light, a difference in spatial distributions of multipolar atom-field interactions may introduce atomic-motion dependent clock uncertainties in optical lattice clocks. We show that the magic wavelength can be defined so as to eliminate the spatial mismatch in electric dipole, magnetic dipole, and electric quadrupole interactions for specific combinations of standing waves by allowing a spatially constant light shift arising from the latter two interactions. Experimental prospects of such lattices used with a blue magic wavelength are discussed.

We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, non-overlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a "velocity comb", a series of narrow equidistant peaks in the velocity space.PACS numbers: 37.10. De, 37.10.Gh, 42.50.Wk Laser cooling is one of the key techniques of modern atomic physics [1][2][3]. Radiative force originates from momentum transfer to atoms from a laser field and subsequent spontaneous emission in random directions. Doppler effect makes the force velocity-dependent. Here we develop a systematic theory of Doppler cooling by a coherent train of short laser pulses (see Fig. 1). A qualitatively new effect comes into play: atomic quantum-mechanical amplitudes induced by subsequent pulses interfere resulting in a periodically varying radiative force as a function of frequency. This structure of the force reflects the comb-like pattern of Fourier image of the pulse train, the so-called frequency comb (FC) [4]. Here we derive the force and show that for sufficiently weak pulses and long atomic lifetimes, each tooth acts as if it were an independent CW laser. In the opposite limit of short lifetimes (short compared to the repetition time between pulses), we recover the force due to an isolated laser pulse. Earlier works on mechanical effects of FCs include proposal involving two-photon transitions [5]. Following proposal [6], pulse trains from mode-locked lasers were also used in cooling experiments [7,8]. To the best of our knowledge no analytical analysis of the FC's radiative force has been attempted so far and it is presented here.Notice that over the past few years the power and spectral coverage of FCs have grown considerably. A fiberlaser-based FC with 10 W average power was demonstrated [9] and the authors argue that the technology is scalable above 10 kW average power. The spectral coverage was expanded from optical frequencies to ultraviolet and to IR spectral regions [10]. These advances pave the road for new applications of FCs, such as the laser cooling.As an application, we consider mapping frequency comb to a "velocity comb". We demonstrate that during pulse-train cooling, continuous velocity distributions gravitate toward a series of sharp (of a typical Doppler width of m/s for strong lines and mm/s for weak lines such as intercombination transition in Sr) peaks in the velocity space. "Velocity combs" could be used for studying velocity-dependent (...

The static hyperpolarizabilities, oscillator-strength-distribution moments S−3 and polarizabilities for S-, P- and D-series of helium and alkali atoms in Rydberg states with principal quantum numbers n between 30 and 70 were calculated in the single-electron Fues' model potential approach. On the basis of the numerical data, three-term polynomials in powers of the effective principal quantum number have been proposed for rapid and accurate evaluations of the indicated characteristics for atoms in arbitrary highly excited states. Numerical values of the fourth-order coefficients in the field-power-series expansions for energies of S1/2-, P1/2,3/2- and D3/2,5/2-states were determined in satisfactory agreement with available data of experiments and theory for rubidium atoms. The numerical data for sodium atoms were used for evaluating the second-order and fourth-order contributions to the electric field magnitude which can tune into double resonance the two-photon transitions between Stark sublevels of the nPJ- and - states via the (n + 1)S1/2-state.

We explore the possibility of decelerating and Doppler cooling an ensemble of tree-level Λ-type atoms by a coherent train of short, non-overlapping laser pulses. We show that Λ-atoms can be Doppler cooled without additional repumping of the population from the intermediate ground state. We derive analytical expression for the scattering force in the quasi-steady-state regime and analyze its dependence on pulse train parameters. Based on this analysis we propose a method of choosing pulse train parameters to optimize the cooling process.

We propose a method of stimulated laser decelerating of diatomic molecules by counter-propagating π-trains of ultrashort laser pulses. The decelerating cycles occur on the rovibrational transitions inside the same ground electronic manifold, thus avoiding the common problem of radiative branching in Doppler cooling of molecules. By matching the frequency comb spectrum of the pulse trains to the spectrum of the R-branch rovibrational transitions we show that stimulated deceleration can be carried out on several rovibrational transitions simultaneously. This enables an increase in the number of cooled molecules with only a single laser source. The exerted optical force does not rely on the decay rates in a system and can be orders of magnitude larger than the typical values of scattering force obtained in conventional Doppler laser cooling schemes.