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We show that the rotational degree of freedom of a polar heteronuclear molecular ion can be cooled through an optical coupling to the collective motional modes of the molecular ion and a simultaneously trapped and laser cooled atomic ion. Since the dissipative part of the rotational cooling is realized through laser cooling of the two-ion systems motional modes, the scheme should be applicable to a large range of molecules. As a test case for our cooling scheme we consider rotational cooling of a MgH+ion trapped with a laser cooled 40Ca+ion.

We propose how to prepare a single molecular ion in a specific internal quantum state in a situation where the molecule is trapped and sympathetically cooled by an atomic ion and where its internal degrees of freedom are initially in thermal equilibrium with the surroundings. The scheme is based on the conditional creation of correlation between the internal state of the molecule and the translational state of the collective motion of the two ions, followed by a projection measurement of this collective mode by atomic ion shelving techniques. We estimate that state preparation in a large number of internal states is possible.

We present an investigation of sub-Doppler effects in a cesium magneto-optical trap. First, a simple one-dimensional theoretical model of the trap is developed for aJg = 1 ?Je = 2 transition. This model predicts the size of the trapped atom cloud and temperature as a function of laser intensity and detuning. In the limit of small magnetic field gradients, the trap temperature is found to be equal to the molasses temperature and a minimum size for the trap is calculated. We then describe several experiments performed in a three-dimensional cesium trap to measure the trap parameters, spring constant, friction coefficient, temperature and density. Whilst the temperature of the trapped atoms is found to be equal to the molasses temperature, in agreement with theory, the trap spring constant is found to be two orders of magnitude smaller than the one-dimensional prediction, a value close to that predicted by Doppler models. The maximum density is found to be on the order of 1012 atoms/cm3 or one atom per optical wavelength on average. When the number of trapped atoms becomes large, the temperature begins to increase dramatically. This excess temperature depends in a very simple way on the atom number, laser intensity and detuning, suggesting that its origin lies in multiple photon scattering within the trap.

Atom lithography provides a new technology that enables one to write directly nanometer scale structures onto a substrate in a parallel process. With this technique the trajectories of atoms are manipulated by light forces that efficiently focus the atoms in a standing light field produced by a laser. By chosing different standing light field configurations one can write different periodic patterns. Theoretical calculations predict a linewidth of the deposited structures in the range of 10–20 nm. The technique is a parallel, direct and species selective process involving low particle energy that prevents any damage of the substrate.

We discuss the fabrication of various one and two-dimensional chromium nanostructures. A chromium atomic beam effusing out of a thermal oven is first transversally laser cooled. This well-collimated beam is then structured and focused by the optical dipole force in a periodic light field. By introducing a substrate at the focus of the atomic beam we are able to capture this pattern directly. We discuss a few applications and challenges of this young lithography technique.

Atom lithography provides a new technology that enables one to write directly nanometer scale structures onto a substrate in a parallel process. With this technique the trajectories of atoms are manipulated by light forces that efficiently focus the atoms in a standing light field produced by a laser. By chosing different standing light field configurations one can write different periodic patterns. Theoretical calculations predict a linewidth of the deposited structures in the range of 10–20 nm. The technique is a parallel, direct and species selective process involving low particle energy that prevents any damage of the substrate.

Large ion crystals containing as many as 105laser-cooled 24Mg+ions arranged in 10 cylindrical shells around a central string have been observed in a linear Paul trap. For smaller crystals consisting of approximately 3500 ions, the varying linear charge densities along the trap axis give rise to well-defined transition regions between the different shell-structures. These structures and the transition regions as a function of linear density are in good agreement with molecular dynamics simulations. The micromotion of the ions in such smaller crystals is also investigated through comparison with MD-simulations. Finally, the degree and progression of ordering in the plasma have been observed for various temperatures and compared with MD-simulations. Good qualitative agreement is again obtained.