| 1. |
- Bogot, Alon, et al.
(författare)
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The mutual neutralization of hydronium and hydroxide
- 2024
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Ingår i: Science. - 0036-8075 .- 1095-9203. ; 383:6680, s. 285-289
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Tidskriftsartikel (refereegranskat)abstract
- Mutual neutralization of hydronium (H3O+) and hydroxide (OH−) ions is a very fundamental chemical reaction. Yet, there is only limited experimental evidence about the underlying reaction mechanisms. Here, we report three-dimensional imaging of coincident neutral products of mutual-neutralization reactions at low collision energies of cold and isolated ions in the cryogenic double electrostatic ion-beam storage ring (DESIREE). We identified predominant H2O + OH + H and 2OH + H2 product channels and attributed them to an electron-transfer mechanism, whereas a minor contribution of H2O + H2O with high internal excitation was attributed to proton transfer. The reported mechanism-resolved internal product excitation, as well as collision-energy and initial ion-temperature dependence, provide a benchmark for modeling charge-transfer mechanisms.
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| 2. |
- Bäckström, Erik, 1983-, et al.
(författare)
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Storing keV negative ions for an hour : The lifetime of the metastable 2P1/2 level in 32S−
- 2015
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 114:14
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Tidskriftsartikel (refereegranskat)abstract
- We use a novel electrostatic ion storage ring to measure the radiative lifetime of the upper level in the 3p 5 P 2 o 1/2 →3p 5 P 2 o 3/2 spontaneous radiative decay in S − 32 to be 503±54 sec . This is by orders of magnitude the longest lifetime ever measured in a negatively charged ion. Cryogenic cooling of the storage ring gives a residual-gas pressure of a few times 10 −14 mbar at 13 K and storage of 10 keV sulfur anions for more than an hour. Our experimental results differ by 1.3σ from the only available theoretical prediction.
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| 3. |
- Chartkunchand, Kiattichart C., et al.
(författare)
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Dianion diagnostics in DESIREE : High-sensitivity detection of C-n(2-) from a sputter ion source
- 2018
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 89:3
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Tidskriftsartikel (refereegranskat)abstract
- A sputter ion source with a solid graphite target has been used to produce dianions with a focus on carbon cluster dianions, C-n(2-), with n = 7-24. Singly and doubly charged anions from the source were accelerated together to kinetic energies of 10 keV per atomic unit of charge and injected into one of the cryogenic (13 K) ion-beam storage rings of the Double ElectroStatic Ion Ring Experiment facility at Stockholm University. Spontaneous decay of internally hot C-n(2-) dianions injected into the ring yielded C-n(2-) anions with kinetic energies of 20 keV, which were counted with a microchannel plate detector. Mass spectra produced by scanning the magnetic field of a 90 degrees analyzing magnet on the ion injection line reflect the production of internally hot C-7(2-) - C-24(2-) dianions with lifetimes in the range of tens of microseconds to milliseconds. In spite of the high sensitivity of this method, no conclusive evidence of C-6(2-) was found while there was a clear C-7(2-) signal with the expected isotopic distribution. This is consistent with earlier experimental studies and with theoretical predictions. An upper limit is deduced for a C-6(2-) signal that is two orders-of-magnitude smaller than that for C-7(2-). In addition, CnO2- and CnCu2- dianions were detected.
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| 4. |
- Chartkunchand, Kiattichart C., et al.
(författare)
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Radiative lifetimes of the bound excited states of Pt-
- 2016
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 American Physical Society.The intrinsic radiative lifetimes of the 5d106sS1/22 and 5d96s2 D3/22 bound excited states in the platinum anion Pt- have been studied at cryogenic temperatures at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University. The intrinsic lifetime of the higher-lying 5d106s S1/22 state was measured to be 2.54±0.10s, while only a lifetime in the range of 50-200 ms could be estimated for the 5d96s2 D3/22 fine-structure level. The storage lifetime of the Pt- ion beam was measured to be a little over 15 min at a ring temperature of 13K. The present study reports the lifetime of an atomic negative ion in an excited bound state with an electron configuration different from that of the ground state.
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| 5. |
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| 6. |
- Danielsson, Mathias, et al.
(författare)
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The cross-section and branching fractions for dissociative recombination of the diacetylene cation C4D2
- 2008
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 273:3, s. 111-116
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report the results of a study on the dissociative recombination (DR) of the diacetylene cation, C4D2+, which has been carried out at the ion storage ring CRYRING in Stockholm, Sweden. The energy-dependent absolute DR cross-section as well as the branching fractions at 0 eV collision energy were measured. The DR cross-section was best fitted using the expression σ(E) = (7.5 ± 1.5) × 10−16 × E−(1.29±0.03) cm2 over the collision energy range 1–100 meV. The thermal rate coefficient was deduced from the cross-section to be α(T) = (1.10 ± 0.15) × 10−6 × (T/300)−(0.79±0.03) cm3/s. The reported branching fractions for C4D2+ agree with previous experiments on the DR of C4H2+ performed at the ASTRID storage ring in Aarhus, Denmark, and furthermore, indicate that the DR of C4D2+ possesses only two channels leading to the following products: C4D + D (75%) and C2D + C2D (25%).
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| 7. |
- Eklund, Gustav, et al.
(författare)
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Cryogenic merged-ion-beam experiments in DESIREE : Final-state-resolved mutual neutralization of Li+ and D-
- 2020
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society (APS). - 2469-9926 .- 2469-9934. ; 102:1
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Tidskriftsartikel (refereegranskat)abstract
- We have developed an experimental technique to study charge-and energy-flow processes in sub-eV collisions between oppositely charged, internally cold, ions of atoms, molecules, and clusters. Two ion beams are stored in separate rings of the cryogenic ion-beam storage facility DESIREE, and merged in a common straight section where a set of biased drift tubes is used to control the center-of-mass collision energy locally in fine steps. Here, we present measurements on mutual neutralization between Li+ and D- where a time-sensitive imaging-detector system is used to measure the three-dimensional distance between the neutral Li and D atoms as they reach the detector. This scheme allows for direct measurements of kinetic-energy releases, and here it reveals separate populations of the 3s state and the (3p + 3d) states in neutral Li while the D atom is left in its ground state 1s. The branching fraction of the 3s final state is measured to be 57.8 +/- 0.7% at a center-of-mass collision energy of 78 +/- 13 meV. The technique paves the way for studies of charge-, energy-, and mass-transfer reactions in single collisions involving molecular and cluster ions in well-defined quantum states.
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| 8. |
- Eklund, Gustav, 1990-
(författare)
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Experiments on mutual neutralization using storage rings with merged ion beams
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents work on merged-beams experiments using the DESIREE facility, which consists of two electrostatic ion-storage rings operated at cryogenic temperatures of about 13 K. The two storage rings have a common straight section, where oppositely charged ions can interact at sub-eV collision energies. The work consists of development of the experimental method, tools for data analysis, and simulations for interpretation of the experimental results. This development has led to the first results from merged-beams experiments at DESIREE. The experiments are performed on mutual neutralization, a collision process where an electron is transferred from a negatively charged ion to a positively charged ion, resulting in two neutral products. This reaction is investigated for three systems: Li+ with D−, Na+ with D−, and Mg+ with D−. The reactions studied are of astrophysical interest, in particular for modeling of stellar atmospheres. The detection of the reaction products is done by using a position- and time-sensitive detector, and from this information it is possible to determine the quantum states involved in the reaction. The branching fractions of the reaction channels are measured and compared to theoretical modeling.
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| 9. |
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| 10. |
- Eklund, Gustav, et al.
(författare)
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Final-state-resolved mutual neutralization of Na+ and D-
- 2021
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 103:3
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Tidskriftsartikel (refereegranskat)abstract
- The present paper reports on a merged-beam experiment on mutual neutralization between Na+ and D-. For this experiment, we have used the DESIREE ion-beams storage-ring facility. The reaction products are detected using a position- and time-sensitive detector, which ideally allows for determination of the population of each individual quantum state in the final atomic systems. Here, the 4s, 3d, and 4p final states in Na are observed and in all cases the D atom is in its ground state 1s S-2. The respective branching fractions of the states populated in Na are determined by fitting results from a Monte Carlo simulation of the experiment to the measured data. The center-of-mass collision energy is controlled using a set of biased drift tubes, and the branching fractions are measured for energies between 80 meV and 393 meV. The resulting branching fractions are found to agree qualitatively with the only available theoretical calculations for this particular system, which are based on a multichannel Landau-Zener approach using dynamic couplings determined with a linear combination of atomic orbitals model.
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