title: Ejection of Coulomb Crystals from a Linear Paul Ion Trap for Ion-Molecule Reaction Studies.
abstract: Coulomb crystals are being increasingly employed as a highly localized source of cold ions for the study of ion-molecule chemical reactions. To extend the scope of reactions that can be studied in Coulomb crystals-from simple reactions involving laser-cooled atomic ions, to more complex systems where molecular reactants give rise to multiple product channels-sensitive product detection methodologies are required. The use of a digital ion trap (DIT) and a new damped cosine trap (DCT) are described, which facilitate the ejection of Coulomb-crystallized ions onto an external detector for the recording of time-of-flight (TOF) mass spectra. This enables the examination of reaction dynamics and kinetics between Coulomb-crystallized ions and neutral molecules: ionic products are typically cotrapped, thus ejecting the crystal onto an external detector reveals the masses, identities, and quantities of all ionic species at a selected point in the reaction. Two reaction systems are examined: the reaction of Ca(+) with deuterated isotopologues of water, and the charge exchange between cotrapped Xe(+) with deuterated isotopologues of ammonia. These reactions are examples of two distinct types of experiment, the first involving direct reaction of the laser-cooled ions, and the second involving reaction of sympathetically-cooled heavy ions to form a mixture of light product ions. Extensive simulations are conducted to interpret experimental results and calculate optimal operating parameters, facilitating a comparison between the DIT and DCT approaches. The simulations also demonstrate a correlation between crystal shape and image shape on the detector, suggesting a possible means for determining crystal geometry for nonfluorescing ions.
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.|Institut für Physikalische Chemie, Georg-August-Universität Göttingen , Tammannstraße 6, D-37077 Göttingen, Germany.
authors.forename: K A E
authors.initials: KA
authors.lastname: Meyer
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: L L
authors.initials: LL
authors.lastname: Pollum
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: L S
authors.initials: LS
authors.lastname: Petralia
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Tauschinsky
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: C J
authors.initials: CJ
authors.lastname: Rennick
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: T P
authors.initials: TP
authors.lastname: Softley
authors.affiliation: Department of Chemistry, University of Oxford, Chemistry Research Laboratory , 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom.
authors.forename: B R
authors.initials: BR
authors.lastname: Heazlewood