1,720,994 research outputs found
Trapping molecules on chips
Get PDFIn the last years, it was demonstrated that neutral molecules can be loaded on a microchip directly from a supersonic beam. The molecules are confined in microscopic traps that can be moved smoothly over the surface of the chip. Once the molecules are trapped, they can be decelerated to a standstill, for instance, or pumped into selected quantum states by laser light or microwaves. Molecules are detected on the chip by time-resolved spatial imaging, which allows for the study of the distribution in the phase space of the molecular ensemble
A Bendable Ion Guide
No full textL'invenzione consiste in un dispositivo flessibile per generare un campo elettrico che trasporti particelle cariche. Il dispositivo ha una struttura elicoidale fatta da un conduttore ricoperto da un dielettrico e il tutto è a sua volta avvolto in una membrana conduttrice. La struttura elicoidale è formata da due elettrodi avvolti a spirale su un cilindro ideale
Formation and photodepletion of cluster ion-messenger atom complexes in a cold ion trap: Infrared spectroscopy of VO+, VO2+, and VO3
No full textA novel experimental technique is described in which radiation from a free electron laser is used to measure infrared spectra of gas-phase cluster ions via vibrational predissociation of the corresponding ion-messenger atom complexes. The weakly bound complexes are formed in a temperature-controllable, radio frequency ion trap. This technique is applied to the study of the vibrational spectroscopy of the monovanadium oxide cluster cations VO+, VO2+, and VO3+. (C) 2003 American Institute of Physics
Taming molecular beams; towards a gas-phase molecular laboratory on a chip
No full textThe manipulation of gas-phase molecules with electric and magnetic fields above a chip is an emerging field of research. Miniaturization of the electric and magnetic field structures allows for the creation of large field gradients and tight traps above the chip. Present-day microelectronics technology enables the integration of complicated tools and devices on a compact surface area. The molecules can be positioned extremely accurately and reproducibly above the chip where they can be held isolated from their environment and where there is excellent access to them. It is expected that several of the gas-phase molecular beam experiments that are currently being done in machines that are up to several meters in length can in the future be performed on a surface area of a few cm 2 and that many new experiments will become possible
Vibrationally exciting molecules trapped on a microchip
No full textPolar molecules in selected quantum states can be guided, decelerated and trapped using electric fields created by microstructured electrodes on a chip. Here we demonstrate that transitions between two vibrational quantum states can be induced while the molecules are trapped above the chip. We use CO molecules, prepared in the J = 1 rotational level of the a a(3)Pi(1), v = 0 state and induce the transition to either the J = 1 or the J = 2 level in the vibrationally excited a(3)Pi(1), v = 1 state with pulsed, narrowband IR radiation. First, the vibrational excitation is studied using CO molecules in a freely propagating molecular beam, in a well-defined homogeneous electric field. Then, we demonstrate that the IR radiation can be coupled to CO molecules that are trapped less than 50 mu m above the chip by guiding molecules in the v = 0 level to the center of the chip where they are pumped to the v = 1 level. The molecules remain trapped and are then guided off the chip and state-selectively detected
Vibrational signatures of hydrogen bonding in the protonated ammonia clusters NH4+(NH3)(1-4)
No full textThe gas phase vibrational spectroscopy of the protonated ammonia dimer N2H7+, a prototypical system for strong hydrogen bonding, is studied in the spectral region from 330 to 1650 cm(-1) by combining infrared multiple photon dissociation and multidimensional quantum mechanical simulations. The fundamental transition of the antisymmetric proton stretching vibration is observed at 374 cm(-1) and assigned on the basis of a six-dimensional model Hamiltonian, which predicts this transition at 471 cm(-1). Photodissociation spectra of the larger protonated ammonia clusters NH4+(NH3)(n) with n=2-4 are also reported for the range from 1050 to 1575 cm(-1). The main absorption features can be assigned within the harmonic approximation, supporting earlier evidence that hydrogen bonding in these clusters is considerably weaker than for n=1
Polyhedral vanadium oxide cages: Infrared spectra of cluster anions and size-induced d electron localization
No full textGas-phase infrared spectroscopy and multidimensional quantum calculations of the protonated ammonia dimer N2H7+
No full textKinetic study of the reaction of vanadium and vanadium-titanium oxide cluster anions with SO2
No full textThe reactivity of mass-selected V4O10- cluster anions towards sulphur dioxide is investigated in an ion trap under multi-collision conditions. Gas phase reaction kinetics are studied as a function of temperature (T-R = 150-275 K). The binding energy of SO2 to V4O10- is obtained by analyzing the experimental low pressure rate constants, employing the Lindemann energy transfer model for association reactions in conjunction with statistical RRKM theory. In addition, infrared multiple photon dissociation spectroscopy is used in conjunction with density functional theory for the structural assignment of the [V4O10-, SO2] complex, revealing a square pyramidal structure with the SO2 molecule incorporated in the vanadium oxide framework. Energy profiles are calculated for the reaction between V4O10- and V6O15- with SO2. Whereas the transition structures along the reaction pathway of V4O10- with SO2 have energies below those of the separated partners, the reaction of V6O15- with SO2 proceeds via a transition structure with energy higher than the educts. The role of cluster size and composition is investigated by studying the reaction kinetics of larger (V6O15- and V8O20-) and titanium doped (V3TiO10- and V2Ti2O10-) vanadium oxide clusters with SO2. The observed cluster size and composition dependencies are discussed
Isomorphous substitution in bimetallic oxide clusters
No full textThe geometric and electronic structure of bimetallic oxide clusters is studied as a function of their composition with gas phase vibrational spectroscopy. Infrared multiple photon dissociation spectra of titanium-vanadium oxide cluster anions are measured in the 500 to 1200 wave number range and assigned on the basis of harmonic frequencies calculated using density functional theory. Singly substituted (V2O5)(n-1)(VTiO5)(-) (n=2-4) cluster anions are shown to form polyhedral caged structures similar to those predicted for their isoelectronic counterparts, the neutral (V2O5)(n) clusters. Upon systematic exchange of V by Ti atoms in V4-nTinO10- (n=1-4), the structure does not change. The stress induced by the isomorphous substitution results in an increased number of unpaired electrons (n-1) for the Ti-rich systems, leading to a quartet ground state for Ti4O10-
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