| 1. |
- Andersson, Jonas, et al.
(författare)
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Auger decay of 4d inner-shell holes in atomic Hg leading to triple ionization
- 2017
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Ingår i: Physical Review A. - : AMER PHYSICAL SOC. - 2469-9926 .- 2469-9934. ; 96
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Tidskriftsartikel (refereegranskat)abstract
- Formation of triply ionized states upon the creation of 4d inner-shell holes in atomic Hg is investigated by using synchrotron radiation of 730 eV photon energy and a versatile multielectron coincidence detection technique in combination with multiconfiguration Dirac-Fock calculations. By carefully selecting Coster-Kronig electrons detected only in coincidence with a 4d photoelectron, the Coster-Kronig spectrum has been extracted and the corresponding branching ratios of the 4d hole have been determined. The results are found to differ from previously established experimental ratios based on electron impact ionization but to agree now better with theory. We also present an Auger cascade analysis of pathways leading to triply ionized states of atomic Hg upon removal of a 4d inner-shell electron.
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| 2. |
- Andersson, Jonas, et al.
(författare)
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Parametrization of energy sharing distributions in direct double photoionization of He
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental results on the characteristic sharing of available excess energy, ranging from 11–221eV, between two electrons in single-photon direct double ionization of He. An effective parametrization of the sharing distributions is presented along with an empirical model that describes the complete shape of the distribution based on a single experimentally determinable parameter. The measured total energy sharing distributions are separated into two distributions representing the shake-off and knock-out parts by simulating the sharing distribution curves expected from a pure wave collapse after a sudden removal of the primary electron. In this way, empirical knock-out distributions are extracted and both the shake-off and knock-out distributions are parametrized. These results suggest a simple method that can be applied to other atomic and molecular systems to experimentally study important aspects of the direct double ionization process.
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| 3. |
- Eland, John H. D., 1941, et al.
(författare)
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Dissociation of multiply charged ICN by Coulomb explosion
- 2016
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 145:7
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Tidskriftsartikel (refereegranskat)abstract
- The fragmentations of iodine cyanide ions created with 2 to 8 positive charges by photoionization from inner shells with binding energies from 59 eV (I 4d) to ca. 900 eV (I 3p) have been examined by multi-electron and multi-ion coincidence spectroscopy with velocity map imaging ion capability. The charge distributions produced by hole formation in each shell are characterised and systematic effects of the number of charges and of initial charge localisation are found. Published by AIP Publishing.
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| 4. |
- Eland, John H. D., 1941, et al.
(författare)
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Double and Triple Ionisation of Isocyanic Acid
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Double and triple ionisation spectra of the reactive molecule isocyanic acid (HNCO) have been measured using multi-electron and ion coincidence techniques combined with synchrotron radiation and compared with high-level theoretical calculations. Vertical double ionisation at an energy of 32.8±0.3eV forms the 3A” ground state in which the HNCO2+ ion is long lived. The vertical triple ionisation energy is determined as 65±1eV. The core-valence double ionisation spectra resemble the valence photoelectron spectrum in form, and their main features can be understood on the basis of a simple and rather widely applicable Coulomb model based on the characteristics of the molecular orbitals from which electrons are removed. Characteristics of the most important dissociation channels are examined and discussed.
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| 5. |
- Eland, John H. D., 1941, et al.
(författare)
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Ion charge-resolved branching in decay of inner shell holes in Xe up to 1200eV
- 2015
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 48:20
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Tidskriftsartikel (refereegranskat)abstract
- Using a new multi-electron multi-ion coincidence apparatus and soft x-ray synchrotron radiation we have determined branching ratios to final Xen+ states with 2 < n < 9 from the 4d(-1), 4p(-1), 4s(-1), 3d(-1) and 3p(-1) Xe+ hole states. The coincident electron spectra give information on the Auger cascade pathways. We show that by judicious choice of coincident electrons, almost pure single charge states of the final ions can be selected.
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| 6. |
- Hult Roos, Andreas, et al.
(författare)
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Abundance of molecular triple ionization by double Auger decay
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Systematic measurements of electron emission following formation of single 1s or 2p core holes in molecules with C, O, F, Si, S and Cl atoms show that overall triple ionization can make up as much as 20% of the decay. The proportion of triple ionization is observed to follow a linear trend correlated to the number of available valence electrons on the atom bearing the initial core hole and on closest neighbouring atoms, where the interatomic distance is assumed to play a large role. The amounts of triple ionization (double Auger decay) after 1s or 2p core hole formation follow the same linear trend, which indicates that the hole identity is not a crucial determining factor in the number of electrons emitted. The observed linear trend for the percentage of double Auger decay follows a predictive line equation of the form DA = 0.415 · Nve + 5.46.
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| 7. |
- Hult Roos, Andreas, et al.
(författare)
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Dissociations of water ions after valence and inner-valence ionization
- 2018
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 149
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Tidskriftsartikel (refereegranskat)abstract
- Energy selected and mass‐resolved electron‐ion coincidence spectra of heavy water have been recorded for ionization energies from 18 to 35 eV. Dissociation from the B2B2 state produces both O+ and D2+ at energies near their thermodynamic thresholds in addition to the known products D+ and OD+. Relative yields of O+, OD+ and D+ in the B2B2 state breakdown diagram are modulated by the vibrational structure of the B‐state population, implying incomplete energy equilibration before fragmentation. Decay from the C‐state produces OD+ in addition to the known O+ and D+. The fragment kinetic energies suggest that O+ and D+ from the C state are products of full atomization of the molecule.
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| 8. |
- Hult Roos, Andreas
(författare)
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Multi-Electron and Multi-Ion Coincidence Spectroscopy of Single-Photon Ionization Processes in Molecules
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents experimental investigations of multi-electron and multi-electron-multi-ion coincidence measurements of samples in the gas phase utilizing a versatile time-of-flight magnetic bottle spectrometer technique. These investigations of multiply ionized atomic and molecular species provide valuable information on, and understanding of, ionization processes and dissociation mechanisms highly relevant to the development of electronic structure theories. Paper I investigated the double valence photoionization spectra of methyl halides. From this study, the lowest onset and vertical double ionization energies were obtained for CH3F, CH3Cl, and CH3I, and used to test an empirical rule-of-thumb for the double ionization of molecules. The study concluded that the apparent inter-charge distance may be derived by applying the rule-of-thumb on molecules similar to the methyl halide structure group. Paper II studied the dissociation of D2O by photoelectron-photoion coincidence measurements. The experiments yielded ion mass-selected photoionization spectra, and dissociation breakdown diagrams, with improved statistics than previous studies of this kind. Minor fragments were detected and modulations in the yield of the fragments were observed of the B2B2 state, with the implication that the fragmented system retains memory of the vibrational structure before the dissociation pathway is irreversibly chosen. Measurements of the C2A1 state revealed high kinetic energy OD+ fragments. Paper III concerned the dissociation mechanisms of ICN upon core site-, and orbital-specific photoionization. The weights of the multiply charged fragmentation channels were obtained from the decay of initial core vacancies, and partial Auger spectra were obtained in coincidence with the doubly charged final products, which revealed the relative extent of the different fragmentation channels in the complete single Auger spectrum of ICN. Papers IV and V investigated the relative abundance of double Auger decay in molecules upon core vacancy formation. The quantity of double compared to single Auger decay was found to surpass 20% in some of the heavier molecules, which is a significant amount and undoubtedly contradicts the past assumption that such processes are negligible. The amount of double Auger decay follows a linear trend with the number of available valence electrons on the nearest neighbouring atoms. It was also found that the 1s or 2p nature of the initial core vacancy had no significant effect on the amount of double Auger decay. The investigation of multiple Auger decay was expanded in Paper VI towards the amount of triple Auger decay in CO and CO2. The quantity of triple compared to single Auger decay in CO and CO2 upon an initial C 1s core vacancy was determined as 0.82% and 1.44%, respectively, and upon an O 1s vacancy as 0.89% and 1.0%, respectively. The percentage of triple Auger decay also follows a linear trend related to the number of available valence electrons.
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| 9. |
- Hult Roos, Andreas, et al.
(författare)
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Relative extent of double and single Auger decay in molecules containing C, N and O atoms
- 2016
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Ingår i: Physical Chemistry Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 18:36, s. 25705-25710
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Tidskriftsartikel (refereegranskat)abstract
- We show that the proportion of double Auger decay following creation of single 1s core holes in molecules containing C, N and O atoms is greater than usually assumed, amounting to about 10% of single Auger decay in many cases. It varies from molecule to molecule, where the size of the molecule has a positive correlation to the amount of double Auger decay. In neon, examined as a related benchmark, the proportion of double Auger decay is similar to that in methane, and is in the order of 5%.
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| 10. |
- Hult Roos, Andreas, et al.
(författare)
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Relative extent of triple Auger decay in CO and CO2
- 2019
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Ingår i: Physical Chemistry Chemical Physics - PCCP. - 1463-9076. ; 21, s. 9889-94
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Tidskriftsartikel (refereegranskat)abstract
- Systematic measurements on single and triple Auger decay in CO and CO2 after the creation of a C 1s or a O 1s core vacancy show that the percentage of triple Auger decay is on the order of 10−2 of the single Auger decay in these molecules. The fractions of triple Auger decay are compared with triple Auger fractions for carbon atoms and some noble gas atoms, and are found to follow a linear trend correlated to the number of valence electrons on the atom with the initial core vacancy and on its closest neighbours. This linear trend for the percentage of triple Auger decay is represented by a predictive equation TA = 0.13·Nve − 0.5.
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