| 1. |
- Andersson, Egil, 1981-, et al.
(författare)
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Core-valence double photoionization of the CS2 molecule
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:9, s. 94305-
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Tidskriftsartikel (refereegranskat)abstract
- Double photoionization spectra of the CS2 molecule have been recorded using the TOF-PEPECO technique in combination with synchrotron radiation at the photon energies h nu=220, 230, 240, 243, and 362.7 eV. The spectra were recorded in the S 2p and C 1s inner-shell ionization regions and reflect dicationic states formed out of one inner-shell vacancy and one vacancy in the valence region. MCSCF calculations were performed to model the energies of the dicationic states. The spectra associated with a S 2p vacancy are well structured and have been interpreted in some detail by comparison to conventional S 2p and valence photoelectron spectra. The lowest inner-shell-valence dicationic state is observed at the vertical double ionization energy 188.45 eV and is associated with a (2p(3/2))(-1)(2 pi(g))(-1) double vacancy. The spectrum connected to the C 1s vacancy shows a distinct line at 310.8 eV, accompanied by additional broad features at higher double ionization energies. This line is associated with a (C 1s)(-1)(2 pi(g))(-1) double vacancy. (C-) 2010 American Institute of Physics. [doi: 10.1063/1.3469812]
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| 2. |
- Andersson, E., et al.
(författare)
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Formation of Kr3+ via core-valence doubly ionized intermediate states
- 2012
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 85:3, s. 032502-
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Tidskriftsartikel (refereegranskat)abstract
- The time-of-flight photoelectron-photoion coincidence technique has been used to study single-photon 3d(9)4p(5) core-valence double ionization of Kr and subsequent Auger decay to triply charged states associated with the 4s(2)4p(3) and 4s(1)4p(4) configurations. The photon energy used was h nu = 150 eV. Multiconfiguration Dirac-Fock calculations were performed both for the doubly ionized intermediate states and the triply ionized final states. The intermediate states of Kr2+ are observed between 120 and 125 eV, whereas the final states of Kr3+ are observed between 74- and 120-eV ionization energy. Assignments of all structures are made based on the present numerical results. The calculated Auger rates give a detailed explanation of the relative line strengths observed.
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| 3. |
- Andersson, Egil, 1981-, et al.
(författare)
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Multielectron coincidence study of the double Auger decay of 3d-ionized krypton
- 2010
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 82:4, s. 043418-
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Tidskriftsartikel (refereegranskat)abstract
- Multielectron coincidence data for triple ionization of krypton have been recorded above the 3d ionization threshold at two photon energies (140 and 150 eV). Three principal transition pathways have been observed, two involving double Auger transitions from Kr+, and one involving single Auger transitions from Kr2+ created by direct single-photon double ionization. The decay of the 3d(9) D-2(5/2,3/2) states in Kr+ has been analyzed in some detail and is found to be strongly dominated by cascade processes where two electrons with well-defined energies are emitted. The decay paths leading to the 4s(2)4p(3) S-4, D-2, and P-2 states of Kr3+ are analyzed and energies of seven intermediate states in Kr2+ are given. A preliminary investigation of the decay paths from Kr+ 3d (9)4p(5)nl shake-up states has also been carried out.
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| 4. |
- Artursson, Elisabet, et al.
(författare)
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Catalytic-site conformational equilibrium in nerve-agent adducts of acetylcholinesterase : Possible implications for the HI-6 antidote substrate specificity
- 2013
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Ingår i: Biochemical Pharmacology. - : Elsevier. - 0006-2952 .- 1356-1839. ; 85:9, s. 1389-1397
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Tidskriftsartikel (refereegranskat)abstract
- Nerve agents such as tabun, cyclosarin and Russian VX inhibit the essential enzyme acetylcholinesterase (AChE) by organophosphorylating the catalytic serine residue. Nucleophiles, such as oximes, are used as antidotes as they can reactivate and restore the function of the inhibited enzyme. The oxime HI-6 shows a notably low activity on tabun adducts but can effectively reactivate adducts of cyclosarin and Russian VX. To examine the structural basis for the pronounced substrate specificity of HI-6, we determined the binary crystal structures of Mus musculus AChE (mAChE) conjugated by cyclosarin and Russian VX and found a conformational mobility of the side chains of Phe338 and His447. The interaction between HI-6 and tabun-adducts of AChE were subsequently investigated using a combination of time resolved fluorescence spectroscopy and X-ray crystallography. Our findings show that HI-6 binds to tabun inhibited Homo sapiens AChE (hAChE) with an IC50 value of 300 μM and suggest that the reactive nucleophilic moiety of HI-6 is excluded from the phosphorus atom of tabun. We propose that a conformational mobility of the side-chains of Phe338 and His447 is a common feature in nerve-agent adducts of AChE. We also suggest that the conformational mobility allow HI-6 to reactivate conjugates of cyclosarin and Russian VX while a reduced mobility in tabun conjugated AChE results in steric hindrance that prevents efficient reactivation.
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| 5. |
- Eland, J. H. D., et al.
(författare)
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Double Core Hole Creation and Subsequent Auger Decay in NH3 and CH4 Molecules
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 105:21, s. 213005-
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Tidskriftsartikel (refereegranskat)abstract
- Energies of the hollow molecules CH42+ and NH32+ with double vacancies in the 1s shells have been measured using an efficient coincidence technique combined with synchrotron radiation. The energies of these states have been determined accurately by high level electronic structure calculations and can be well understood on the basis of a simple theoretical model. Their major decay pathway, successive Auger emissions, leads first to a new form of triply charged ion with a core hole and two valence vacancies; experimental evidence for such a state is presented with its theoretical interpretation. Preedge 2-hole-1-particle (2h-1p) states at energies below the double core-hole states are located in the same experiments and their decay pathways are also identified.
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| 6. |
- Eland, John H. D., et al.
(författare)
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Homonuclear site-specific photochemistry by an ion-electron multi-coincidence spectroscopy technique
- 2012
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 548, s. 90-94
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Tidskriftsartikel (refereegranskat)abstract
- By combining multi-particle coincidence detection of electrons and ions with ionisation by soft X-ray synchrotron radiation we demonstrate an effective tool for atomic spectroscopy and site-specific photochemistry. Its most novel capability is application to molecular fragmentation after K-shell vacancy production in atoms distinguished only by their chemical environment.
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| 7. |
- Eland, John H. D., et al.
(författare)
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Single and multiple photoionisation of H(2)S by 40-250 eV photons
- 2011
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 13:41, s. 18428-18435
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Tidskriftsartikel (refereegranskat)abstract
- Multi-electron coincidence measurements on photoionisation of H(2)S have been carried out at photon energies from 40 to 250 eV. They quantify molecular field effects on the Auger process in detail and are in good agreement with the existing theory. Spectra of core-valence double ionisation of H(2)S are presented and partially analysed. Auger decays from the core-valence states produce triply charged product spectra with unexplained and surprising intensity distributions. Triple ionisation by the double Auger process from 2p hole states shows little effect of the molecular field splitting, but includes a substantial contribution from cascade processes, some involving dissociation in intermediate states. The onset of triple ionisation at the molecular geometry is determined as 61 +/- 0.5 eV.
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| 8. |
- Eland, J. H. D., et al.
(författare)
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Spectra of the triply charged ion CS23+ and selectivity in molecular Auger effects
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 132:10, s. 104311-
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Tidskriftsartikel (refereegranskat)abstract
- Spectra of triply charged carbon disulphide have been obtained by measuring, in coincidence, all three electrons ejected in its formation by photoionization. Measurements of the CS23+ ion in coincidence with the three electrons identify the energy range where stable trications are formed. A sharp peak in this energy range is identified as the (2)Pi ground state at 53.1 +/- 0.1 eV, which is the lowest electronic state according to ab initio molecular orbital calculations. Triple ionization by the double Auger effect is provisionally divided, on the basis of the pattern of energy sharing between the two Auger electrons into contributions from direct and cascade Auger processes. The spectra from the direct double Auger effect via S 2p, S 2s, and C 1s hole states contain several resolved features and show selectivity based on the initial charge localization and on the identity of the initial state. Triple ionization spectra from single Auger decay of S 2p-based core-valence states CS22+ show retention of the valence holes in this Auger process. Related ion-electron coincidence measurements give the triple ionization yields and the breakdown patterns in triple photoionization at selected photon energies from 90 eV to above the inner shell edges.
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| 9. |
- Eland, J. H. D., et al.
(författare)
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Triple ionisation of methane by double Auger and related pathways
- 2010
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 485:03-jan, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- Triple ionisation of methane by decay of the singly charged ion with a 1s vacancy produces a trication spectrum starting near 70 eV binding energy. Vibrational excitation in the initial hole state broadens and shifts the triple ionisation bands. Ionisation through core-valence doubly ionised states gives lower triple ionisation onsets and changes the spectral intensity pattern in accordance with retention of the initial valence holes in course of the double Auger effect. The double Auger effects occur both directly and as cascades, the different pathways producing different electron distributions and final state spectra.
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| 10. |
- Eland, John H. D., et al.
(författare)
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Triple ionization of CO(2) by valence and inner shell photoionization
- 2011
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 135:13, s. 134309-
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Tidskriftsartikel (refereegranskat)abstract
- Spectra of triply ionized CO(2) have been obtained from photoionization of the molecule using soft x-ray synchrotron light and an efficient multi-electron coincidence technique. Although all states of the CO(2)(+++) trication are unstable, the ionization energy for formation of molecular ions at a geometry similar to that of the neutral molecule is determined as 74 +/- 0.5 eV.
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