Cold ion traps

Wang X-B, Woo H-K, Wang L-S. (2005) Vibrational cooling in a cold ion trap VibrationaUy resolved photoelectron spectroscopy of cold C q Anions. J. Chem. Phys. 123 051106-1-051106-4. 

Asvany O, Ricken O, Muller HSP, Wiedner MC, Giesen TF, Schlemmer S (2008) High-resolution rotational spectroscopy in a cold ion trap H2D and D2H. Phys Rev Lett 100 233004... 

Along similar lines, Choi et al. combined a cold Paul trap with a TOFMS, first cooling it to 150 K [135] and later to 10 K [136]. WhUe coupling a quadmpole irai trap with TOFMS was not new, having first been demonstrated by Lubman and coworkers in the early 1990s [137], Choi et al. were the first to do this with a cold ion trap and use it for photofragment spectroscopy [138]. Using protonated tyrosine as a benchmark [46], they estimated the internal temperature of their ions to be on the order of 50 K. 

In all those measurement instruments which use the ionization of gas molecules as the measurement principle (cold-cathode and hot-cathode ionization vacuum gauges), strong magnetic leakage fields or electrical potentials can have a major influence on the pressure indication. At low pressures it is also possible for wall potentials which deviate from the cathode potential to influence the ion trap current. 

Jansen and co-workers [97] have described on-line TD-GC-FTIR. In the TD-GC-FTIR system a thermal desorption (TD) cold trap injector is used for the temperature-controlled outgassing of the samples with a maximum temperature of 350 °C. The volatile components are transferred to the cold trap by the carrier gas and preconcentrated. After completion of the outgassing process the cold trap is heated very quickly, causing on-column injection of the trapped components onto the gas chromatograph. The technique has recently been extended to include an ion-trap MS. 

The competition between elimination and substitution channels when an alkyl halide is allowed to react with a nucleophile in the gas phase is a difficult problem to tackle, since in most gas-phase experiments only the ionic products of reaction are monitored (a few exceptions are reported below). Thus, for example, when w-propyl bromide is allowed to react with methoxide ion in the gas phase, the bromide ion produced can arise either by elimination (a) or by substitution (b) and the two pathways cannot be distinguished from the ions alone (Scheme 34). In this specific case it was possible to establish that the reaction follows exclusively the elimination channel through collection and analysis of the neutral products246. The experiments were performed on a FA apparatus configured with a novel cold finger trap coupled to a GC/MS system. Material collected by the trap was separated by capillary gas chromatography and the individual components identified by their retention times and El mass spectra246. 

All samples are analysed for Cd, Pb, Cr against standard calibration curves prepared from 0.0, 0.5, 2.5, 5.0 and lO.Oppm of each metal in 0.25 M HNO3. The ultrasonic nebuliser is used for the determination of Cd, Pb and Cr while the continuous cold vapour trap method is used for the determination of Hg. The recovery of each metal is determined for each metal. The Hg forms the vapour ion of the metal in solution after reduction with SnCl2(Sn2+ + Hg2+ > Sn4+ + Hg°) and the metallic mercury is swept to the plasma torch by the argon gas. This method is sensitive for Hg and has the advantage that it removes the analyte from the main solution and has very low limits of detection. 

In spite of impressive experimental demonstrations of basic quantum information effects in a number of different mesoscopic solid state systems, such as quantum dots in semiconductor microcavities, cold ions in traps, nuclear spin systems, Josephson junctions, etc., their concrete implementation is still at the proof-of-principle stage [1]. The development of materials that may host quantum coherent states with long coherence lifetimes is a critical research problem for the nearest future. There is a need for the fabrication of quantum bits (qubits) with coherence lifetimes at least three-four orders of magnitude longer than it takes to perform a bit flip. This would involve entangling operations, followed by the nearest neighbor interaction over short distances and quantum information transfer over longer distances. 

The main effect of background gas (residual gas or reactant gas) is due to ion/neutral collisions of background gas with the cold atomic and molecular ions. Some collisions are manifested by a sudden disappearance of fluorescence light because the ions acquire sufficient kinetic energy to move away from the ion-trap axis. They are, however, typically not expelled from the pseudo-potential well of depth ca 1 eV and, after a while, they become laser-cooled sufficiently to be re-aligned along the ion-trap axis and they resume fluorescing. 

ION TRAPPING AND PRODUCTION OF COLD MOLECULES 18.3.1 Radio-Frequency Ion Traps... 

The ability to reversibly deform cold multicomponent crystals by static quadrupole potentials is interesting for several reasons. It allows for (1) a controlled ejection of heavier ion species from the trap (see below), (2) a complete radial separation of lower-mass SC ions from the LC ions, and (3) opening up the possibility of studying trap modes of oscillation of ellipsoidal crystals, in particular of multispecies crystals. Conversely, a precise measurement of the trap modes of oscillation of cold ion crystals allows for the identification of even small anisotropies of the effective trap potential, which is important for precision measurement applications and the characterization of systematic effects, such as offset potentials [45]. 

The cold ion-neutral reactions most easily studied are those involving the laser-cooled atomic ions. The first examples studied were the formation of cold trapped CaO+ ions by the reaction between laser-cooled Ca+ ions and neutral O2 [32,76]. Using the CaO+ ions formed, the back-reaction CaO+ + CO -> Ca+ + CO2 was observed [32], Furthermore, the formation of cold trapped MgH+ by the reaction between laser-cooled Mg+ ions and neutral H2 was also observed [30]. Reaction rates and branching ratios were deduced. 

They indicate that R6G+ will absorb cooling laser light and might fragment as a consequence, while GAH+ will not. This is indeed observed on the cold ions. Figures 18.31 and 18.32 show photofragmentation of cold ( 0.1 K) trapped R6G+ and GAH+ ions. Rhodamine 101 ions were also found to photodissociate in the presence of the cooling laser. 

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