We present experimental data on the dissociative recombination (DR) and the dissociative excitation (DE) of O2+ in its electronic and vibrational ground state using a heavy ion storage ring. The absolute DR cross section has been determined over an electron collision energy range from 1 meV to 3 eV. The thermal DR rate coefficient is derived; α(Te)=2.4×10−7(300/Te)0.70±0.01 cm3 s−1, for T>200 K. The threshold for DE was observed near its energetic threshold of 6.7 eV. The DE cross section curve has a maximum of 3×10−16 cm2 near 15 eV. We have determined the branching fractions to the different dissociation limits and present atomic quantum yields for the DR process between 0 to 300 meV collision energy. The quantum yield of O(1D) is found to be 1.17±0.05, largely independent of the electron energy. Arguments are presented that the branching fraction to O(3P)+O(1S) is negligible. The branching fraction to the O(1S)+O(1D) is smaller than 0.06 and varies strongly as a function of collision energy. The O(1S) quantum yield is a strong function of electron temperature. Hence, the relative strength of the green, O(1S), and the red, O(1D), airglows may be used as a measure of the electron temperature of the upper atmosphere. A qualitative explanation is given of the consequences of nonadiabatic interactions in the dissociation step of the DR process.

Dissociative recombination and excitation of O2+: Cross sections, product yields and implications for studies of ionospheric airglows

We describe a system combining an ion beam trap and a low energy electron target in which the interaction between electrons and vibrationally cold molecular ions and clusters can be studied. The entire system uses only electrostatic fields for both trapping and focusing, thus being able to store particles without a mass limit. Preliminary results for the electron impact neutralization of C2− ions and aluminum clusters are presented.

Electrostatic ion beam trap for electron collision studies

The efficiency of electron cooling can be improved by adiabatically expanding the electron beam in a decreasing magnetic field, thereby lowering the transverse electron temperature. An electron beam expanded by a factor of 10 has been implemented at the CRYRING electron cooler, decreasing the transverse electron temperature from 100 to 10 meV. This has resulted in an increased drag force between ions and electrons and in large reductions of cooling times. Also, the energy resolution in electron-ion recombination experiments at low relative energy has increased by a factor of 10.

Electron cooling with an ultracold electron beam.

We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate “rings” and merged over a common straight section The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology

The double electrostatic ion ring experiment: A unique cryogenic electrostatic storage ring for merged ion-beams studies

The exploration of the unique properties of stored and cooled beams of highly-charged ions as provided by heavy-ion storage rings has opened novel and fascinating research opportunities in the realm of atomic and nuclear physics research. Since the late 1980s, pioneering work has been performed at the CRYRING at Stockholm (Abrahamsson et al. 1993) and at the Test Storage Ring (TSR) at Heidelberg (Baumann et al. 1988). For the heaviest ions in the highest charge-states, a real quantum jump was achieved in the early 1990s by the commissioning of the Experimental Storage Ring (ESR) at GSI Helmholtzzentrum fur Schwerionenforschung (GSI) in Darmstadt (Franzke 1987) where challenging experiments on the electron dynamics in the strong field regime as well as nuclear physics studies on exotic nuclei and at the borderline to atomic physics were performed. Meanwhile also at Lanzhou a heavy-ion storage ring has been taken in operation, exploiting the unique research opportunities in particular for medium-heavy ions and exotic nuclei (Xia et al. 2002).

/pdf/physics-book-cryring-esr-51aj6htcu3.pdf

Physics book: CRYRING@ESR

The ultra high vacuum system of Cryring

The experimental program at CRYRING storage ring began shortly after the installation of the electron cooler in May 1992. The performance of the ion sources and the ring is reported. Results of electron cooling are reviewed and a method to improve the efficiency of electron cooling is presented. >

/pdf/the-first-year-with-electron-cooling-at-cryring-l8ujrt0gyd.pdf

The first year with electron cooling at CRYRING

CRYRING is a small synchrotron and storage ring equipped with electron cooling. Highly charged ions from the electron beam ion source CRYSIS or singly charged ions from the plasmatron source MINIS are injected via an RFQ into the ring. The facility is in the commissioning phase. Full design energy has been achieved and electron cooling demonstrated both for atomic and molecular ions. The experimental program started in August with two projects, dissociative recombination of H+3 ions and radiative recombination to deuterons. The status as of September 20, 1992, is reported.

CRYRING — a synchrotron, cooler and storage ring

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The ultra high vacuum system of Cryring

The first year with electron cooling at CRYRING

CRYRING — a synchrotron, cooler and storage ring