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  • 1.
    Alvarez Ruiz, Jesus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Melero-Garcia, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki, Antti
    Coreno, M.
    Erman, Peter
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics.
    Richter, R.
    Synchrotron radiation induced fluorescence spectroscopy of SF62005In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, p. 387-Article in journal (Refereed)
    Abstract [en]

    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.

  • 2.
    García, Emilio Melero
    et al.
    KTH, Superseded Departments, Physics.
    Álvarez Ruiz, Jesús
    KTH, Superseded Departments, Physics.
    Erman, Peter
    KTH, Superseded Departments, Physics.
    Kivimäki, Antti Eerik
    KTH, Superseded Departments, Physics.
    Rachlew-Källne, Elisabeth
    KTH, Superseded Departments, Physics.
    Rius Riu, Jaume
    KTH, Superseded Departments, Physics.
    Stankiewicz, Marek
    KTH, Superseded Departments, Physics.
    Veseth, V.
    Neutral dissociation of superexcited states in nitric oxide2003In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 293, no 1, p. 65-73Article in journal (Refereed)
    Abstract [en]

    Near-infrared dispersed fluorescence measurements of 13 different atomic multiplets of neutral atomic fragments from photon induced neutral dissociation processes in NO are reported. For excitation of the molecules narrow band synchrotron photons of energy 17.2-25.8 eV were used. Neither Rydberg series nor other molecular states in NO known so far can account for the collected data. From ab initio calculations we try to obtain more information regarding the NO precursor states, and the mechanism behind the observed neutral dissociation.

  • 3.
    Jakubowska, Katarzyna
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Vall-llosera, Gemma
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki, Antti
    CNR-INFM, Laboratorio Nazionale TASC.
    Coreno, Marcello
    CNR-INFM, Laboratorio Nazionale TASC.
    Melero García, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Stankiewicz, Marek
    Instytut Fizyki Im. Mariana Smoluchowskiego, Uniwersytet Jagielloński.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Lyman and Balmer emission following core excitations in methane and ammonia molecules2007In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 40, no 8, p. 1489-1500Article in journal (Refereed)
    Abstract [en]

    The intensities of hydrogen Lyman-alpha and Balmer series emission lines as a result of photoexcitation of free CH4 and NH3 molecules at the C 1s and N 1s edges have been measured. For methane, the total fluorescence yield in the visible region ( 300 - 650 nm) was also recorded. Excitation functions of the Balmer lines show relative intensity enhancement of Balmer-beta emission in comparison with Balmer-alpha at higher core- to- Rydberg excitations. The Lyman-alpha emission intensity, in general, follows the relations observed in the corresponding total ion yield measurements. Additionally, the Balmer-gamma and -delta yields were measured for ammonia molecules and they show intensity maxima at photon energies shifted closer to the N 1s threshold than Balmer-alpha and -beta. A quantum defect analysis is performed to find out which core excitations are responsible for this enhanced intensity. Dissociation pathways leading to the emission in H atoms are discussed.

  • 4. Kivimäki, A.
    et al.
    de Simone, M.
    Coreno, M.
    Feyer, V.
    Garcia, Emilio Melero
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Ruiz, Jesús Alvarez
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Richter, R.
    Prince, K. C.
    Observation of core-hole double excitations in water using fluorescence spectroscopy2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 1, p. 014503-Article in journal (Refereed)
    Abstract [en]

    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.

  • 5.
    Kivimäki, Antti
    et al.
    KTH, Superseded Departments, Physics.
    Alvarez Ruiz, Jesus
    KTH, Superseded Departments, Physics.
    Erman, Peter
    KTH, Superseded Departments, Physics.
    Hatherly, Paul
    Melero Garcia, Emilio
    KTH, Superseded Departments, Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Rius i Riu, Jaume
    KTH, Superseded Departments, Physics.
    Stankiewicz, Marek
    An energy resolved electron-ion coincidence study near the S 2p thresholds of the SF6 molecule2003In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 36, no 4, p. 781-791Article in journal (Refereed)
    Abstract [en]

    The fragmentation dynamics of the SF6 molecule following the excitations of S 2p electrons into unoccupied molecular orbitals has been studied using the energy-resolved electron-ion coincidence technique. Fragmentation patterns were found to depend on the particular excitation and on the electronic state of the molecular ion. The spectator resonant Auger decay at the 2p --> 6a(1g) resonance induces changes in the ion distributions as compared to direct photoionization. Furthermore, coincidence spectra related to the same Auger structure display different ion abundances at the 2t(2g) and 4e(g) shape resonances. Differences were also found in the Auger decay spectra. These findings give further support for the previously suggested many-electron character of the 4e(g) shape resonance.

  • 6. Kivimäki, Antti
    et al.
    Coreno, M.
    Richter, R.
    Alvarez Ruiz, Jesus
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Melero Garcia, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    De Simone, M.
    Feyer, V.
    Vall Llosera, Gemma
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Prince, K. C
    Fluorescence emission following core excitations in the water molecule2006In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 5, p. 1101-1112Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Melero García, Emilio
    KTH, Superseded Departments, Physics.
    Fragmentation studies of small molecules using synchrotron radiation2004Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents experimental data on the fragmentationof gas phase sulfur hexafluoride (SF6) and deutheromethane(CD4) molecules after their interaction with synchrotronradiation in the energy range of 70-200 eV. The data wasobtained using coincidence spectroscopy between energy resolvedelectrons and ions (EREICO).

    Degradation of the molecular bond upon selective ionizationof different molecular orbitals has been studied by measuringionic fragments in coincidence with energy selected electrons.Besides the direct ionisation of the orbitals also the indirectprocess, in which the hole is created by the decay of a highlyenergetic core-excited state, was studied. The differencesdetected in the fragmentation after the direct and indirectionisation of a selected orbital can be related, in some cases,with the relaxation of the nuclei in the potential energysurface of the core excited state during its lifetime, thusproviding information on the neutral core excited state.

    An experimental set-up capable of photon inducedfluorescence spectroscopy (PIFs) studies of core excitedmolecules in the visible range has been constructed. Thistechnique can yield complementary information to the EREICOdata about the energy distribution in the fragmentation sincethe internal energy of excited emitted fragments that decay inthe visible can be measured. It also allows the detection ofpossible neutral fragments.

  • 8.
    Melero Garcia, Emilio
    KTH, School of Engineering Sciences (SCI), Physics.
    Synchrotron radiation spectroscopy of molecular dynamics beyond the valence shell2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis presents experimental results on molecular spectroscopy of gas phase molecules using synchrotron radiation. It deals mainly with dynamical processes following resonant excitation of electrons from core and inner-valence shells of the following systems H2O, H2, SF6 and CD4. In order to reach these deep electrons and excite them photons in the energy range from 25 to 550 eV were used, depending on the particular system.

    Two experimental techniques are used. Photon induced fluorescence spectroscopy is used to study the fluorescence emission of fragments after the decay of resonant coreexcited states for the water molecule, and after doubly excited states and resonant excitations of inner-shell electrons for H2 and SF6 respectively. Only the emission in the visible and near infrared range (300-900nm) and the Lyman-α transitions are measured. Energy resolved electron-ion coincidence is used for the study of the fragmentation of CD4 and SF6 after selective ionisation of one of the outer-valence orbitals. In the case of CD4 the fragmentation is compared for the cases in which the ionisation is done directly, or through participator Auger decay of different resonantly core-excited states.

  • 9.
    Melero Garcia, Emilio
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Alvarez Ruiz, Jesus
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics.
    Rachlew, Elisabet
    KTH, School of Engineering Sciences (SCI), Physics.
    Erman, Peter
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki et al., Antti
    Fluorescence study of doubly excited states of molecular hydrogen2006In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, no 2, p. 205-213Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Melero Garcia, Emilio
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki, Antti
    Pettersson, L. M.
    KTH, School of Engineering Sciences (SCI), Physics.
    Alvarez Ruiz,, Jesús
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Coreno, M.
    De Simone, M.
    Richter, R.
    Prince, K. C.
    Fluorescence Emission of Excited Hydrogen Atoms after Core Excitation of Water Vapor2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Physical review letters, Vol. 96, p. 063003-Article in journal (Refereed)
    Abstract [en]

    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.

  • 11.
    Rius Riu, Jaime
    et al.
    KTH, Superseded Departments, Physics.
    Melero Garcia, Emilio
    KTH, Superseded Departments, Physics.
    Alvarez Ruiz, Jesus
    KTH, Superseded Departments, Physics.
    Erman, Peter
    KTH, Superseded Departments, Physics.
    Hatherly, Paul
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Stankiewicz, Marek
    KTH, Superseded Departments, Physics.
    Core-excitation-induced dissociation in CD4 after participator Auger decay2003In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 68, no 2Article in journal (Refereed)
    Abstract [en]

    The fragmentation of the CD4 molecule after selective ionization of the 1t(2) and 2a(1) electrons with photons from 70 to 290 eV has been studied with the energy-resolved electron-ion coincidence technique. The mass spectra acquired in coincidence with 1t(2) electrons reveal CD4+, CD3+, and CD2+ fragments, depending on the excitation energy used. The production of CD3+ is strongly enhanced after C 1s excitation to different core excited states, with respect to the production observed after direct ionization of the 1t(2) orbital. This enhancement is correlated with the changes of the molecular geometry when it relaxes from the core-excited state.

  • 12. Stankiewicz, M.
    et al.
    Riu, Jaume Rius I.
    KTH, Superseded Departments, Physics.
    Ruiz, J. Alvarez
    KTH, Superseded Departments, Physics.
    Erman, Peter
    KTH, Superseded Departments, Physics.
    Hatherly, P.
    Kivimaki, Antti
    KTH, Superseded Departments, Physics.
    Garcia, E. Melero
    KTH, Superseded Departments, Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Relaxation dynamics of SF6 studied by energy-resolved electron ion coincidence technique2004In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 137-40, p. 369-375Article in journal (Refereed)
    Abstract [en]

    The mass spectra from the SF6 molecule acquired by energy-resolved electron ion coincidence (EREICO) technique using (1t(1g) + [5t(1u),1t(2u)]), (3e(g) + 1t(2g)), 4t(1u), and 5a(1g) electrons after both valence and S 2p(-1) 6a(1g) core excitation reveal a strong selectivity in the dissociation from these states. From the comparison of the obtained spectra, the influence of the core-excited state in the relaxation pathway of the molecule is studied. The S 2p --> 6a(1g) core excitation does not affect the relaxation dynamics after participator Auger decay to the (1t(1g) + [5t(1u),1t(2u)])(-1) and (4t(1u))(-l) states, but it alters the relaxation dynamics after participator Auger decay to the (3e(g) + 1t(2g))(-1) and (5a(1g))(-1) states with respect to the decay processes after direct excitation of the same orbitals. These observations point to core excitation induced dissociation in the SF6 molecule.

  • 13. Stankiewicz, Marek
    et al.
    Melero García, Emilio
    KTH, Superseded Departments, Physics.
    Álvarez Ruiz, Jesus
    KTH, Superseded Departments, Physics.
    Eman, Peter
    KTH, Superseded Departments, Physics.
    Hathery, Paul
    Kivimäki, Antti
    KTH, Superseded Departments, Physics.
    Rachlew, Elisabeth
    KTH, Superseded Departments, Physics.
    Rius i Riu, Jaume
    KTH, Superseded Departments, Physics.
    Experimental station for gas phase fluorescence spectroscopy2004In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, no 7, p. 2402-2408Article in journal (Refereed)
    Abstract [en]

    The details of an experimental setup for gas phase atomic and molecular fluorescence measurements using synchrotron radiation are described in this article. The most significant part of the apparatus is an optical arrangement, which allows for simultaneous measurements of dispersed as well as total fluorescence intensity using an effusive gas jet and an inbuilt gas cell assembled in a convenient plug and measure configuration. The first measurements concerning fluorescence of the N-2 molecule around the N 1s edge obtained with this setup are presented.

  • 14.
    Vall-llosera, Gemma
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Melero García, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Kivimäki, Antti
    CNR-INFM, Laboratorio Nazionale TASC.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Coreno, Marcello
    CNR-IMIP, Montelibretti.
    de Simone, Monica
    CNR-INFM, Laboratorio Nazionale TASC.
    Richter, Robert
    Sincrotrone Trieste, Basovizza.
    Prince, Kevin C.
    Sincrotrone Trieste, Basovizza.
    Fluorescence emission from photo-fragments after resonant S 2p excitations in H2S2007In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 9, no 3, p. 389-395Article in journal (Refereed)
    Abstract [en]

    Visible-UV fluorescence emission of gas-phase hydrogen sulfide, H2S, has been studied at the S 2p edge with synchrotron radiation excitation. Dispersed fluorescence measurements in the wavelength range 300 - 900 nm were taken at several photon energies corresponding to the excitations of the S 2p electrons to the unoccupied molecular and Rydberg orbitals. The spectra reveal fluorescence from the H, S, S+, HS and HS+ photo-fragments. H is found to be the strongest emitter at Rydberg excitations, while the emission from S+ is dominant at the molecular resonances and above the S 2p ionization thresholds. The intensities of hydrogen Lyman-alpha (122 nm), Balmer-alpha (656 nm), Balmer-beta (486 nm) transitions as well as the visible-UV total fluorescence yield (300 - 900 nm) and the total ion yield were measured by scanning the photon energy in small steps across the S 2p edge. The different Balmer lines show some sensitivity to the specific core excitations, which is, however, not so strong as that recently observed in the water molecule.

  • 15.
    Vall-llosera, Gemma
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Álvarez Ruiz, Jesús
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Erman, Peter
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Melero García, Emilio
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Rachlew, Elisabeth
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Menmuir, Sheena
    KTH, School of Engineering Sciences (SCI), Physics, Atomic and Molecular Physics.
    Stankiewicz, Marek
    Instytut Fizyki, Jageillonian University.
    The npσ,π to EF emission systems in D2 studied by selective excitation2005In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, no 6, p. 659-664Article in journal (Refereed)
    Abstract [en]

    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).

1 - 15 of 15
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