| 1. |
- Alvarez Ruiz, Jesus, et al.
(författare)
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Synchrotron radiation induced fluorescence spectroscopy of SF6
- 2005
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38, s. 387-
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Tidskriftsartikel (refereegranskat)abstract
- The fluorescence of gaseous SF6 was investigated after excitation with 25-80eV synchrotron radiation photons. The total UV-Vis-near IR fluorescence yield was recorded and interpreted in terms of inner valence excitations/ionizations and double excitations in SF6. Dispersed fluorescence measurements in the 400-1000 nm spectral range reveal excited S, S+, F and F+ fragments as solely responsible for the emission. The fluorescence intensity of some of the observed atomic transitions was monitored as a function of the excitation energy. Single, double and triple excitations as well as direct ionizations and shake-ups are proposed as the triggering processes responsible for the creation of the emitting fragments.
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| 2. |
- Kivimäki, Antti, et al.
(författare)
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Fluorescence emission following core excitations in the water molecule
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:5, s. 1101-1112
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Tidskriftsartikel (refereegranskat)abstract
- Photon-induced fluorescence spectroscopy has been used to study the fragmentation of the water molecule at the O 1s is edge. Fluorescence emission has been observed from the neutral fragments H, O and OH as well as from the ionic fragments O+ and OH+. The extracted fluorescence yields of the H Lyman-alpha emission and O 2p(3)(S-4)3p(P-3) -> 2p(3)(S-4)3s(S-3) transitions show the same structures as the total ion yield spectrum but with different relative intensities. The most intense fluorescence emission is restricted to the region of the core excitations, while above the O 1s ionization limit the signal is much weaker (in the case of H) or below the detection limit (O, OH and OH+). The fluorescence emission is concluded to follow from the following general cascade: the core-excited states decay by resonant Auger transitions, the final states reached undergo dissociation into ionic and neutral fragments, and fluorescence occurs from excited fragments. In the case of the OH (A(2)Sigma(+) -> X-2 Pi) emission, the decay of core-excited states through soft x-ray emission may also be responsible for the observed fluorescence.
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| 3. |
- Kivimäki, A., et al.
(författare)
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Observation of core-hole double excitations in water using fluorescence spectroscopy
- 2007
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:1, s. 014503-
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Tidskriftsartikel (refereegranskat)abstract
- The hydrogen Lyman-alpha, Balmer-alpha, and Balmer-beta emission has been measured from the H2O molecule at photon energies exceeding the 1s ionization threshold. Fluorescence emission is shown to be a sensitive probe to neutral core-hole doubly excited states and singly ionized 1s shake-up states that are embedded in the core ionization continuum. In addition, the photoabsorption spectrum of the water molecule in the energy range of the double excitations has been measured with better statistics than previously.
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| 4. |
- Melero Garcia, Emilio, et al.
(författare)
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Fluorescence Emission of Excited Hydrogen Atoms after Core Excitation of Water Vapor
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 96, s. 063003-
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Tidskriftsartikel (refereegranskat)abstract
- The Balmer emission from atomic hydrogen has been recorded across the resonances at the oxygen K edge of the water molecule using synchrotron radiation excitation. The emission is observed to be strongest at excitations to Rydberg resonances. The observations are interpreted using a qualitative model for the dynamics of the core-to-Rydberg excited molecule. The model links the quantum state of the core-excited water molecule via resonant Auger decay and subsequent dissociation to the state of the fluorescing hydrogen atom.
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| 5. |
- Melero Garcia, Emilio, et al.
(författare)
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Fluorescence study of doubly excited states of molecular hydrogen
- 2006
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 39:2, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- Photodissociation of molecular hydrogen has been investigated by means of fluorescence spectroscopy using synchrotron radiation. Balmer-alpha emission from atomic hydrogen photofragments was collected in the 20-55 eV excitation energy range. Experimental data are interpreted in terms of excitation and fragmentation of neutral doubly excited states and excited ionic states with the aid of recent theoretical model calculation.
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| 6. |
- Ruiz, Jesus Alvarez, et al.
(författare)
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VUV photon induced fluorescence study of SF5CF3
- 2006
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 8:44, s. 5199-5206
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Tidskriftsartikel (refereegranskat)abstract
- The interaction of SF5CF3 with vacuum-UV radiation has been investigated by photon induced fluorescence spectroscopy. Total fluorescence yield and dispersed fluorescence spectra of SF5CF3 were recorded in the 200-1000 nm fluorescence window. In all cases, the fluorescence spectra resemble those of CF3X (X H, F, Cl, and Br) molecules. At photon energies below 20 eV, the emission is attributed to the excited CF3 and CF2 fragments. The threshold for the CF3 emission is 10.2 +/- 0.2 eV, giving an upper limit estimate for the SF5-CF3 bond dissociation energy of 3.9 +/- 0.3 eV. The excitation functions of the CF3 and CF2 emissions were measured in the photon energy range 13.6-27.0 eV. The resonant structures observed in SF5CF3 are attributed to electronic transitions from valence to Rydberg orbitals, following similar assignments in CF3X molecules. The photoabsorption spectrum of SF5CF3 shows features at the same energies, indicating a strong contribution from Rydberg excitations.
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| 7. |
- Vall-llosera, Gemma, et al.
(författare)
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The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase
- 2008
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:4, s. 044316-1-044316-12
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Tidskriftsartikel (refereegranskat)abstract
- Near edge x-ray absorption fine structure spectra have been measured and interpreted by means of density functional theory for five different azabenzenes (pyridine, pyridazine, pyrimidine, pyrazine, and s-triazine) in the gas phase. The experimental and theoretical spectra at the N 1s and C 1s edges show a strong resonance assigned to the transition of the 1s electron in the respective N or C atoms to the lowest unoccupied molecular orbital with pi* symmetry. As opposed to the N 1s edge, at the C 1s edge this resonance is split due to the different environments of the core hole atom in the molecule. The shift in atomic core-level energy due to a specific chemical environment is explained with the higher electronegativity of the N atom compared to the C atom. The remaining resonances below the ionization potential (IP) are assigned to transitions to valence/Rydberg orbitals with mixed pi*/sigma* character. Upon N addition, a reduction of intensity is observed in the Rydberg region at both edges as compared to the intensity in the continuum. Above the IP one or more resonances are seen and ascribed here to transitions to sigma* orbitals. Calculating the experimental and theoretical Delta(pi) term values at both edges, we observe that they are almost the same within +/- 1 eV as expected for isoelectronic bonded pairs. The term values of the pi* and sigma* resonances are discussed in terms of the total Z number of the atoms participating in the bond.
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| 8. |
- Vall-llosera, Gemma, et al.
(författare)
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The npσ,π to EF emission systems in D2 studied by selective excitation
- 2005
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 38:6, s. 659-664
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Tidskriftsartikel (refereegranskat)abstract
- The np sigma 1 Sigma(u)(+) and np pi (1)Pi(u) states in D-2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF (1)Sigma(g)(+) state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P and R branches relative to the Q branch were found to vary strongly in the np pi (1)Pi(u)(+)-EF(1)Sigma(g)(+) bands indicating the existence of predissociations of np pi (1)Pi(u)(+) levels above the dissociation limit D(1s) + D(2l).
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