| 1. |
- Anderson, Emma K., et al.
(författare)
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Decays of excited silver-cluster anions Agn, n=4 to 7, in the Double ElectroStatic Ion Ring ExpEriment
- 2018
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Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - 2469-9926 .- 2469-9934. ; 98:2
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous decays of small, hot silver-cluster anions Ag-n(-), n = 4-7, have been studied using one of the rings of the Double ElectroStatic Ion Ring ExpEriment (DESIREE). Observation of these decays over very long time scales is possible due to the very low residual gas pressure (similar to 10(-14)) and cryogenic (13 K) operation of DESIREE. The yield of neutral particles from stored beams of Ag-6(-) and Ag-2(-) anions were measured for 100 milliseconds and were found to follow single power-law behavior with millisecond time-scale exponential cutoffs. The Ag-4(-) and Ag-5(-) anions were stored for 60 s and the observed decays show two-component power-law behaviors. We present calculations of the rate constants for electron detachment from and fragmentation of Ag-4(-) and Ag-5(-). In these calculations, we assume that the internal energy distribution of the clusters are flat and with this we reproduce the early steep parts of the experimentally measured decay curves for Ag-4(-) and Ag-5(-) which extends to tens and hundreds of milliseconds, respectively. The fact that the calculations reproduce the early slopes of Ag-4(-) and Ag-5(-), which differ for the two cases, suggests that it is the changes in fragmentation rates with internal cluster energies of Ag-4(-) and Ag-5(-) rather than conditions in the ion source that determine this behavior. Comparisons with the measurements strongly suggest that the neutral particles detected in these time domains originate from Ag-4(-) -> Ag-3(-) + Ag and Ag-5(-) -> Ag-3(-) +Ag-2 fragmentation processes.
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| 2. |
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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. |
- Hansen, Klavs, 1958, et al.
(författare)
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Spontaneous decay of small copper-cluster anions Cun− (n=3–6), on long time scales
- 2017
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 95:2
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the spontaneous neutral particle emission from copper-cluster anions (Cun −, n = 3–6) stored at cryogenic temperatures in one of the electrostatic ion storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The measured rate of emission from the stored Cu3 − ions follows a single power-law decay for about 1 ms but then decreases much more rapidly with time. The latter behavior may be due to a decrease in the density of available final states in Cu3 as the excitation energies of the decaying ions approach the electron detachment threshold. The emissions from Cu4 −, Cu5−, and Cu6− are well described by sums of two power laws that are quenched by radiative cooling of the stored ions with characteristic times between a few and hundreds of milliseconds. We relate these two-component behaviors to populations of stored ions with higher and lower angular momenta. In a separate experiment, we studied the laser-induced decay of Cu6− ions that were excited by 1.13- or 1.45-eV photons after 46 ms of storage.
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| 6. |
- Kamińska, Magdalena, et al.
(författare)
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Lifetime of the bound excited level in Ni
- 2016
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Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 93:1
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Tidskriftsartikel (refereegranskat)abstract
- The intrinsic lifetime of the upper level in the bound-bound 3d(9) 4s(2) D-2(3/2) -> 3d(9) 4s(2) D-2(5/2) radiative transition in Ni- was measured to be 15.1 +/- 0.4 s. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the Ni- ion beam was measured to be close to 5 min at a ring temperature of 13 K.
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| 7. |
- Schmidt, Henning T., et al.
(författare)
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Rotationally Cold OH- Ions in the Cryogenic Electrostatic Ion-Beam Storage Ring DESIREE
- 2017
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 119:7
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Tidskriftsartikel (refereegranskat)abstract
- We apply near-threshold laser photodetachment to characterize the rotational quantum level distribution of OH- ions stored in the cryogenic ion-beam storage ring DESIREE at Stockholm University. We find that the stored ions relax to a rotational temperature of 13.4 +/- 0.2 K with 94.9 +/- 0.3% of the ions in the rotational ground state. This is consistent with the storage ring temperature of 13.5 +/- 0.5 K as measured with eight silicon diodes but in contrast to all earlier studies in cryogenic traps and rings where the rotational temperatures were always much higher than those of the storage devices at their lowest temperatures. Furthermore, we actively modify the rotational distribution through selective photodetachment to produce an OH- beam where 99.1 +/- 0.1% of approximately one million stored ions are in the J = 0 rotational ground state. We measure the intrinsic lifetime of the J = 1 rotational level to be 145 +/- 28 s.
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