We present experimental and theoretical studies of coherent excitation of magnetic sublevels in nD states of cesium that cross in an external electric field. Coherent excitation of mFmagnetic sublevels of hyperfine F levels with DeltamF= plusmn2 leads to resonances in the linearly polarized laser induced fluorescence (LIF), while coherent excitation of magnetic sublevels with DeltamF= plusmn1 leads to alignment to orientation conversion (AOC). From the resonance signals we were able to measure atomic constants, such as the hyperfine constant A and the tensor polarizability alpha2(Auzinsh et al., 2006). AOC involves the deformation of the spatial distribution of an atom's angular momentum and is of interest as a background in certain types of experiments that search for a permanent electric dipole moment (EDM) of the electron.
We explore ways to use the ability to measure the populations of individual magnetic sublevels to improve the sensitivity of magnetic field measurements and measurements of atomic electric dipole moments (EDMs). When atoms are initialized in the m=0 magnetic sublevel, the shot-noise-limited uncertainty of these measurements is 1/2F(F+1) smaller than that of a Larmor precession measurement. When the populations in the even (or odd) magnetic sublevels are combined, we show that these measurements are independent of the tensor Stark shift and the second order Zeeman shift. We discuss the complicating effect of a transverse magnetic field and show that when the ratio of the tensor Stark shift to the transverse magnetic field is sufficiently large, an EDM measurement with atoms initialized in the superposition of the stretched states can reach the optimal sensitivity.
The dipole-dipole interaction strongly couples ultracold highly excited atoms, known as Rydberg atoms, and is the dominant mechanism for energy exchange among such atoms on microsecond time scales. I present the results of experiments that investigate this interaction using rubidium atoms excited to Rydberg states with an all-diode laser system. In the first of these, high resolution dipole-dipole interaction spectra for different magnetic sublevels of the 32d5/2 state are collected and analyzed. In the second experiment, ultracold rubidium atoms are implusively excited to coherent superpositions of three closely spaced |mj|sublevels of the 32d5/2 state in a weak electric field. The magnitude of the field sets the energy level spacing between these states, and hence the frequency of the phase dependent oscillations resulting from interference in resonant energy exchange processes. In the third experiment, the dipole-dipole interaction induced resonant energy exchange between columns of ultracold rubidium Rydberg atoms is imaged using a new technique involving selective field ionization with a spatially sensitive ion detector.