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We study the immersion of a ferromagnetic nanowire within a nematic liquid crystal using a lattice Boltzmann algorithm to solve the full three-dimensional equations of hydrodynamics. We present an algorithm for including a moving boundary, to simulate a nanowire, in a lattice Boltzmann simulation. The nematic imposes a torque on a wire that increases linearly with the angle between the wire and the equilibrium direction of the director field. By rotation of these nanowires, one can determine the elastic constants of the nematic. [ABSTRACT FROM AUTHOR]

In a crossed beam atomic energy transfer experiment, relative cross sections are measured between initial and final magnetic substates of atomic orbitals in a three vector correlation experiment. A pulsed laser beam prepares Ca(4s5p 1P1) in a single magnetic sublevel |j1mi> with respect to the laser polarization vector. Subsequent collision with He at a well-defined relative velocity yields Ca(4s5p 3P2). The near-resonant Ca(4s5p 3P2) is probed by a second polarized pulsed laser, revealing its magnetic sublevel |j2mf> distribution with respect to the probe laser polarization vector. The experiment is analyzed in the collision frame where the direction of the initial relative velocity vector serves as the quantization axis. In this frame, the initial and final Ca states are characterized by substates |j1m1> and |j2m2>, respectively. Fourteen collision frame cross sections are needed to describe the energy transfer completely. Eight of these cross sections are real and positive (conventional type—describing population transfer) and six are complex (coherence type—containing phase information). By symmetry, only 15 unique parameters for the real and imaginary parts of the cross sections are required, nine of which are obtained here using linear polarizations and collinear laser beams.Possible cases for circularly polarized light are also tabulated; measurement of these cases would provide several more parameters. For initial parallel preparation of the 1P1 p orbital with respect to the relative velocity (m1=0), the final 3P2 state is highly aligned in the m2=±1 and m2=±2 sublevels. Initial preparation of the p orbital perpendicular to the relative velocity vector (m1=±1) produces an aligned 3P2 state with greater population in the m2=0 and m2=±1 sublevels compared to the m2=±2 sublevels. Using the coherence information and symmetry, orientation cross sections are obtained into the m2=±1 sublevels (i.e., m preserving... [ABSTRACT FROM AUTHOR]

The Ca(4p2 1D2) state is prepared in a two-step excitation with linearly polarized lasers. Two different angular wave functions are selected, Y2,0 or (Y2,-1-Y2,1)/, by using parallel or perpendicular laser polarizations, respectively. Subsequent collision with a rare gas atom (He, Ne, Ar, Kr, or Xe) populates the near-resonant Ca(3d4p 1F3) state. The dependence of the collisional energy transfer process is measured as a function of the alignment of the initial 1D2 state wave function with respect to the average relative velocity vector. The laser-selected Y2,0 and (Y2,-1-Y2,1)/ angular wave functions display dramatically different alignment dependences, which are understood by an analysis of the rotation properties of these wave functions. The relative contributions to the cross section of the individual 1D2 sublevels, ML=0, ±1, and ±2, are extracted, and these vary considerably depending on the rare gas. For He, the ML=±2 sublevel (asymptotic Δ molecular state) contributes the most to the total cross section, while for all the other rare gases, the ML=0, ±1 sublevels (asymptotic Σ and Π molecular states, respectively) are more important. The contribution of the ML=0 sublevel increases smoothly with increasing mass of the rare gas collision partner, becoming the largest contributor for Xe. [ABSTRACT FROM AUTHOR]