A continuous source of translationally cold dipolar molecules

The Stark interaction of polar molecules with an inhomogeneous electric field is exploited to select slow molecules from a room-temperature reservoir and guide them into an ultrahigh vacuum chamber. A linear electrostatic quadrupole with a curved section selects molecules with small transverse and longitudinal velocities. The source is tested with formaldehyde (H2CO) and deuterated ammonia (ND3). With H2CO a continuous flux is measured of approximately 10^9/s and a longitudinal temperature of a few K. The data are compared with the result of a Monte Carlo simulation.Comment: 4 pages, 4 figures v2: small changes in the abstract, text and references. Figures 1 & 2 regenerated to prevent errors in the pd

Ground state and elementary excitations of single and binary Bose-Einstein condensates of trapped dipolar gases

We analyze the ground-state properties and the excitation spectrum of Bose-Einstein condensates of trapped dipolar particles. First, we consider the case of a single-component polarized dipolar gas. For this case we discuss the influence of the trapping geometry on the stability of the condensate as well as the effects of the dipole-dipole interaction on the excitation spectrum. We discuss also the ground state and excitations of a gas composed of two antiparallel dipolar components.Comment: 12 pages, 9 eps figures, final versio

A storage ring for neutral molecules

Contains fulltext : 33306.pdf (publisher's version ) (Open Access)Time-varying inhomogeneous electric fields can be used to manipulate the motion of neutral molecules in phase-space, i.e., position-momentum space, via their electric dipole moment. A theoretical background is given on the motion of the molecules in phase-space. As the forces exerted on the molecules by the electric fields are conservative, Liouville's theorem dictates that the phase-space density remains constant. Starting from a pulsed supersonic expansion a package of neutral molecules can be decelerated, focused, cooled and confined using appropriately designed (time-varying) electric fields. In this way, deuterated ammonia molecules (ND_3) have been stored in a storage ring at very low translational temperatures and have been detected after more than 50 round trips. Temperatures on the order of 300 microKelvin have been obtained. A first study has been performed to investigate the dynamics of the molecules while they are stored in the ring. By splitting the ring in sections and inserting so-called bunchers it should be possible to detect the molecules after many more round trips. Numerical calculations are presented showing that such a sectional ring is experimentally feasibleRU Radboud Universiteit Nijmegen, 20 januari 2005Promotor : Meijer, G.J.M.118 p

Dynamics of neutral molecules stored in a ring

Contains fulltext : 60361.pdf (publisher's version ) (Open Access)A decelerated beam of neutral ammonia molecules is injected into an electrostatic storage ring. Electrostatic lenses are used to map the emittance of the decelerator onto the acceptance of the ring. The tangential velocity spread of the package of molecules in the ring is set to less than 1 m/s. The package of molecules can be observed for more than 50 distinct round trips, corresponding to 40 m in circular orbit and almost 0.5 s storage time, sufficiently long for a first investigation of its transversal motion in the ring

Longitudinal focusing and cooling of a molecular beam

Contains fulltext : 98934.pdf (publisher's version ) (Open Access

Deceleration and trapping of ammonia using time-varying electric fields

Contains fulltext : 98925.pdf (publisher's version ) (Open Access

Electrostatic trapping of ammonia molecules

Contains fulltext : 98954.pdf (publisher's version ) (Closed access

Tactile device based on opto-mechanical actuation of liquid crystal elastomers

Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. Thus, actuation can be produced on demand, forcing these phase changes. Here, we present a refreshable tactile device based on the opto-mechanical properties of liquid crystalline elastomers (LCE) with the capability to represent Braille characters and simplified graphical information. The actuators designed are based on the use of the stress gradient generated in the elastomer under illumination to exert a force on movable components. Additionally, hardware implementation and a communication software interface were developed to provide end users with a complete solution. Displacements of 0.8 mm with measured forces of up to 40 mN were reached without material degradation, proving not only the viability of the device but also the potential applications of this type of actuator.Scopu

Nematic opto-mechanical actuators for the fabrication of refreshable tactile systems

Nematic elastomers are promising materials for the fabrication of actuators due to their ability to reversibly contract and expand during phase transitions triggered by external stimuli. We present a refreshable tactile system based on the opto-mechanical properties of liquid-crystalline elastomers (LCE) composites, with the capability to represent Braille characters and graphic information. The actuators designed are based on the stress gradient generated in the elastomer under illumination to exert a force on movable components. Hardware implementation and communication software interface were developed too to provide end users with a complete solution. First tests prove not only the viability of the device, but also the potential applications of this type of actuators.Scopu