| 1. |
- Andersson, Pontus, 1971, et al.
(författare)
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Nearly complete isobar suppression by photodetachment
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 1089-7550 .- 0021-8979. ; 107:2
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of selective suppression of negative ions by photodetachment in a gas-filled radio frequency quadrupole ion cooler was investigated with a new detection method. A neodymium doped yttrium aluminum garnet laser beam at 1064 nm was used to remove Co− ions in the radio frequency quadrupole cooler and the remaining ions were then probed by photodetachment and neutral particle detection. More than 99.99% suppression of the Co− ions was observed. Under identical conditions, only 20% of a Ni− beam was suppressed. The results demonstrate that this isobar suppression technique can lead to nearly complete elimination of certain isobaric contaminants in negative ion beams, opening up new experimental possibilities in nuclear and atomic research and accelerator mass spectrometry.
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| 2. |
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| 3. |
- Diehl, C., et al.
(författare)
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Ion optical design of a collinear laser-negative ion beam apparatus
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:5
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Tidskriftsartikel (refereegranskat)abstract
- An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ≃ 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M/ΔM≅800 for molecular ions and M/ΔM≅400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.
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| 4. |
- Leopold, Tobias, et al.
(författare)
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Feasibility of photodetachment isobar suppression of WF5- with respect to HfF5
- 2014
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806 .- 1873-2798. ; 359, s. 12-18
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Tidskriftsartikel (refereegranskat)abstract
- The feasibility of using laser photodetachment as a means for isobar suppression in accelerator mass spectrometry has been investigated for the special case of HfF5-/WF5-. A method for absolute photodetachrnent cross section measurements was applied and the cross sections of tungsten pentafluoride and hafnium pentafluoride negative ions were measured. The measurements indicate that the photodetachment cross section for WF5- is at least 100 times larger than for HfF5- at the wavelength of the fourth harmonic of the Nd:YAG laser at 266 nm. The absolute cross section for WF5- at this photon energy was found to be (2.8 +/- 0.3) x 10(-18) cm(2), while an upper limit of 2 x 10(-2) cm(2) was obtained for the HfF5- cross section. The measured cross sections indicate that an optical filtering scheme for isobar suppression in accelerator mass spectrometry for the case of Hf-182 should be feasible. (C) 2013 Elsevier B.V. All rights reserved.
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| 5. |
- Lindahl, Anton, 1982, et al.
(författare)
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Depletion of the excited state population in negative ions using laser photodetachment in a gas-filled RF quadrupole ion guide
- 2010
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:11
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Tidskriftsartikel (refereegranskat)abstract
- The depopulation of excited states in beams of negatively charged carbon and silicon ions was demonstrated using collisional detachment and laser photodetachment in a radio-frequency quadrupole ion guide filled with helium. The high-lying, loosely bound D-2 excited state in C- was completely depleted through collisional detachment alone, which was quantitatively determined within 6%. For Si-the combined signal from the population in the P-2 and D-2 excited states was only partly depleted through collisions in the cooler. The loosely bound P-2 state was likely to be completely depopulated, and the more tightly bound D-2 state was partly depopulated through collisions. 98(2)% of the remaining D-2 population was removed by photodetachment in the cooler using less than 2 W laser power. The total reduction of the excited population in Si-, including collisional detachment and photodetachment, was estimated to be 99(1)%. Employing this novel technique to produce a pure ground state negative ion beam offers possibilities of enhancing selectivity, as well as accuracy, in high-precision experiments on atomic as well as molecular negative ions.
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| 6. |
- Lindahl, Anton, 1982, et al.
(författare)
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Experimental studies of partial photodetachment cross sections in K- below the K(7 2P) threshold
- 2012
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Ingår i: Physical Review A. - : American Physical Society. - 1050-2947. ; 85:3
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Tidskriftsartikel (refereegranskat)abstract
- A collinear beams apparatus has been used to determine photodetachment cross sections for K− in the photon energy range 4.250–4.360 eV. State-selective detection, utilizing a resonance ionization scheme, was applied to measure partial cross sections for those channels which leave the residual K atoms in the excited 7 2S, 5 2F, and 5 2G states. The energy region studied encompassed the openings of the aforementioned channels, as well as the channel that leaves the K atom in the 7 2P state. Two previously unobserved resonances were seen in all three partial cross sections between the K(5 2G) and K(7 2P) thresholds. It is shown that a more reliable determination of resonance parameters can be made if the same resonances are observed in several channels. In the region below the K(5 2F) threshold, three previously observed resonances were investigated [Kiyan et al. Phys. Rev. Lett. 84 5979 (2000)]. A greatly increased modulation of the signal was obtained by detecting in the K(7 2S) channel instead of the K(5 2S) channel used in the previous study. Furthermore, the shapes of the cross sections in the threshold regions are discussed. A detailed description of the apparatus and the experimental procedure employed is presented in the paper.
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| 7. |
- Lindahl, Anton, 1982, et al.
(författare)
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Observation of thresholds and overlapping resonances below the 10(2)P(1/2) and P-2(3/2) thresholds in the photodetachment of Cs
- 2013
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Ingår i: Physical Review A. - 1050-2947. ; 88:5
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Tidskriftsartikel (refereegranskat)abstract
- A collinear beam apparatus has been used to study photodetachment of Cs-. Partial cross sections were measured using state-selective detection based on a resonance ionization scheme. Several resonances were observed in the Cs(10(2)S), Cs(6 2F), Cs(6 2G), and Cs(6 2H) final-state channels below the Cs(10(2)P3/2) channel opening. A model was developed to account for the interference between overlapping resonances. This model is essentially a generalization of the Fano [U. Fano, Phys. Rev. 124, 1866 (1961)] and Shore [B. W. Shore, Phys. Rev. 171, 43 (1968)] parametrizations for single resonances. Resonance parameters were extracted by fitting the model to the data sets. The openings of the Cs(10(2)S) and Cs(6 2F) channels, where the polarizabilities of the atomic states are large and positive, showed rapid onsets. In the case of the Cs(6(2)G) and Cs(6(2)H) channels, on the other hand, the photodetachment cross sections increased slowly with energy. For the Cs(6(2)H) channel this is the expected behavior, since it is the result of a large and negative polarizability of the 6(2)H state. In addition, the excitation of the Cs(6(2)H) state with respect to the Cs ground state was found to be 28 356.3(2) cm(-1), in agreement with a previous experiment.
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| 8. |
- Lindahl, Anton, 1982, et al.
(författare)
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The electron affinity of tungsten
- 2010
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Ingår i: The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 60:2, s. 219-222
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Tidskriftsartikel (refereegranskat)abstract
- The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm-1 by observing the onset of the process when W- ions in the 6S5/2 ground state are photodetached producing neutral W atoms in the 5D0 ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W-.
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| 9. |
- Lindahl, Anton, 1982, et al.
(författare)
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Threshold behaviour in photodetachment of K-
- 2012
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Ingår i: Journal of Physics: Conference Series (XXVII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2011)). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:PART 2
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Konferensbidrag (refereegranskat)abstract
- A photodetachment experiment has been performed with the formation of atoms in highly excited states of high positive and negative polarizabilities. A semiclassical model has been developed to describe the effect of the repulsive polarization potential in the vicinity of the photoreaction threshold.
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| 10. |
- Lindahl, Anton, 1982, et al.
(författare)
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Threshold Photodetachment in a Repulsive Potential
- 2012
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007. ; 108:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first experimental observation of a new threshold behavior observed in the 5 2G partial channel in photodetachment of K-. It arises from the repulsive polarization interaction between the detached electron and the residual K(5 2G) atom, which has a large negative dipole polarizability. In order to account for the observation in the K(5 2G) channel, we have developed a semiclassical model that predicts an exponential energy dependence for the cross section. The measurements were made with collinear laser-ion beams and a resonance ionization detection scheme.
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