Laser Spinning of Nanotubes: A path to fast-rotating microdevices

We show that circularly polarized light can spin nanotubes with GHz frequencies. In this method, angular moments of infrared photons are resonantly transferred to nanotube phonons and passed to the tube body by "umklapp" scattering. We investigate experimental realization of this ultrafast rotation in carbon nanotubes, levitating in an optical trap and undergoing mechanical vibrations, and discuss possible applications to rotating microdevices.Comment: 4 pages, 3 Postscript figure

Comprehensive rate coefficients for electron collision induced transitions in hydrogen

Energy-changing electron-hydrogen atom collisions are crucial to regulating the energy balance in astrophysical and laboratory plasmas and relevant to the formation of stellar atmospheres, recombination in H-II clouds, primordial recombination, three-body recombination and heating in ultracold and fusion plasmas. Computational modeling of electron-hydrogen collision has been attempted through quantum mechanical scattering state-to-state calculations of transitions involving low-lying energy levels in hydrogen (with principal quantum number n < 7) and at large principal quantum numbers using classical trajectory techniques. Analytical expressions are proposed which interpolates the current quantum mechanical and classical trajectory results for electron-hydrogen scattering in the entire range of energy levels, for nearly all temperature range of interest in astrophysical environments. An asymptotic expression for the Born cross-section is interpolated with a modified expression derived previously for electron-hydrogen scattering in the Rydberg regime using classical trajectory Monte Carlo simulations. The derived formula is compared to existing numerical data for transitions involving low principal quantum numbers, and the dependence of the deviations upon temperature is discussed.Comment: To appear in The Astrophysical Journa

Potential energy curves for the interaction of Ag(5s) and Ag(5p) with noble gas atoms

We investigate the interaction of ground and excited states of a silver atom with noble gases (NG), including helium. Born-Oppenheimer potential energy curves are calculated with quantum chemistry methods and spin-orbit effects in the excited states are included by assuming a spin-orbit splitting independent of the internuclear distance. We compare our results with experimentally available spectroscopic data, as well as with previous calculations. Because of strong spin-orbit interactions, excited Ag-NG potential energy curves cannot be fitted to Morse-like potentials. We find that the labeling of the observed vibrational levels has to be shifted by one unit