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  • 1.
    Alvarez Ruiz, Jesus
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Melero-Garcia, Emilio
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Kivimäki, Antti
    Coreno, M.
    Erman, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Rachlew, Elisabeth
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Richter, R.
    Synchrotron radiation induced fluorescence spectroscopy of SF62005Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, s. 387-Artikkel i tidsskrift (Fagfellevurdert)
    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, Tidigare Institutioner, Fysik.
    Álvarez Ruiz, Jesús
    KTH, Tidigare Institutioner, Fysik.
    Erman, Peter
    KTH, Tidigare Institutioner, Fysik.
    Kivimäki, Antti Eerik
    KTH, Tidigare Institutioner, Fysik.
    Rachlew-Källne, Elisabeth
    KTH, Tidigare Institutioner, Fysik.
    Rius Riu, Jaume
    KTH, Tidigare Institutioner, Fysik.
    Stankiewicz, Marek
    KTH, Tidigare Institutioner, Fysik.
    Veseth, V.
    Neutral dissociation of superexcited states in nitric oxide2003Inngår i: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 293, nr 1, s. 65-73Artikkel i tidsskrift (Fagfellevurdert)
    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. Kivimäki, A.
    et al.
    de Simone, M.
    Coreno, M.
    Feyer, V.
    Garcia, Emilio Melero
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Ruiz, Jesús Alvarez
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Richter, R.
    Prince, K. C.
    Observation of core-hole double excitations in water using fluorescence spectroscopy2007Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, nr 1, s. 014503-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 4.
    Kivimäki, Antti
    et al.
    KTH, Tidigare Institutioner                               , Fysik.
    Alvarez Ruiz, Jesus
    KTH, Tidigare Institutioner                               , Fysik.
    Erman, Peter
    KTH, Tidigare Institutioner                               , Fysik.
    Hatherly, Paul
    Melero Garcia, Emilio
    KTH, Tidigare Institutioner                               , Fysik.
    Rachlew, Elisabeth
    KTH, Tidigare Institutioner                               , Fysik.
    Rius i Riu, Jaume
    KTH, Tidigare Institutioner                               , Fysik.
    Stankiewicz, Marek
    An energy resolved electron-ion coincidence study near the S 2p thresholds of the SF6 molecule2003Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 36, nr 4, s. 781-791Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 5. Kivimäki, Antti
    et al.
    Coreno, M.
    Richter, R.
    Alvarez Ruiz, Jesus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Melero Garcia, Emilio
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    De Simone, M.
    Feyer, V.
    Vall Llosera, Gemma
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Prince, K. C
    Fluorescence emission following core excitations in the water molecule2006Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, nr 5, s. 1101-1112Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 6.
    Melero Garcia, Emilio
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Alvarez Ruiz, Jesus
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Rachlew, Elisabet
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Erman, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Kivimäki et al., Antti
    Fluorescence study of doubly excited states of molecular hydrogen2006Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 39, nr 2, s. 205-213Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 7.
    Melero Garcia, Emilio
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Kivimäki, Antti
    Pettersson, L. M.
    KTH, Skolan för teknikvetenskap (SCI), Fysik.
    Alvarez Ruiz,, Jesús
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Coreno, M.
    De Simone, M.
    Richter, R.
    Prince, K. C.
    Fluorescence Emission of Excited Hydrogen Atoms after Core Excitation of Water Vapor2006Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Physical review letters, Vol. 96, s. 063003-Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 8.
    Rius Riu, Jaime
    et al.
    KTH, Tidigare Institutioner                               , Fysik.
    Melero Garcia, Emilio
    KTH, Tidigare Institutioner                               , Fysik.
    Alvarez Ruiz, Jesus
    KTH, Tidigare Institutioner                               , Fysik.
    Erman, Peter
    KTH, Tidigare Institutioner                               , Fysik.
    Hatherly, Paul
    Rachlew, Elisabeth
    KTH, Tidigare Institutioner                               , Fysik.
    Stankiewicz, Marek
    KTH, Tidigare Institutioner                               , Fysik.
    Core-excitation-induced dissociation in CD4 after participator Auger decay2003Inngår i: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 68, nr 2Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 9. Stankiewicz, M.
    et al.
    Riu, Jaume Rius I.
    KTH, Tidigare Institutioner, Fysik.
    Ruiz, J. Alvarez
    KTH, Tidigare Institutioner, Fysik.
    Erman, Peter
    KTH, Tidigare Institutioner, Fysik.
    Hatherly, P.
    Kivimaki, Antti
    KTH, Tidigare Institutioner, Fysik.
    Garcia, E. Melero
    KTH, Tidigare Institutioner, Fysik.
    Rachlew, Elisabeth
    KTH, Tidigare Institutioner, Fysik.
    Relaxation dynamics of SF6 studied by energy-resolved electron ion coincidence technique2004Inngår i: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 137-40, s. 369-375Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 10. Stankiewicz, Marek
    et al.
    Melero García, Emilio
    KTH, Tidigare Institutioner                               , Fysik.
    Álvarez Ruiz, Jesus
    KTH, Tidigare Institutioner                               , Fysik.
    Eman, Peter
    KTH, Tidigare Institutioner                               , Fysik.
    Hathery, Paul
    Kivimäki, Antti
    KTH, Tidigare Institutioner                               , Fysik.
    Rachlew, Elisabeth
    KTH, Tidigare Institutioner                               , Fysik.
    Rius i Riu, Jaume
    KTH, Tidigare Institutioner                               , Fysik.
    Experimental station for gas phase fluorescence spectroscopy2004Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, nr 7, s. 2402-2408Artikkel i tidsskrift (Fagfellevurdert)
    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.

  • 11.
    Vall-llosera, Gemma
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Gao, Bin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Kivimäki, A.
    CNR-INFM, Laboratorio Nazionale TASC, Trieste.
    Coreno, M.
    CNR-IMIP, Montelibretti, Rome.
    Álvarez Ruiz, Jesús
    CSIC, Inst Quim Fis Rocasolano, Dept Quim Laser, Madrid.
    de Simone, M.
    CNR-INFM, Laboratorio Nazionale TASC, Trieste.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Rachlew, Elisabeth
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    The C 1s and N 1s near edge x-ray absorption fine structure spectra of five azabenzenes in the gas phase2008Inngår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 128, nr 4, s. 044316-1-044316-12Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 12.
    Vall-llosera, Gemma
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Álvarez Ruiz, Jesús
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Erman, Peter
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Melero García, Emilio
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Rachlew, Elisabeth
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Menmuir, Sheena
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Atom- och molekylfysik.
    Stankiewicz, Marek
    Instytut Fizyki, Jageillonian University.
    The npσ,π to EF emission systems in D2 studied by selective excitation2005Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, nr 6, s. 659-664Artikkel i tidsskrift (Fagfellevurdert)
    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).

  • 13.
    Álvarez Ruiz, Jesús
    KTH, Tidigare Institutioner, Fysik.
    Synchrotron radiation induced fluorescence spectroscopy of gas phase molecules2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    A new experimental set-up for gas phase fluorescence studies using synchrotron radiation has been designed and constructed to perform simultaneously total and dispersed fluorescence measurements.

    Neutral photodissociation of CO has been investigated after excitation with 19-26 eV photons. Fluorescence from 3p 3P, 3p 3S and 3p 1D excited states in carbon was recorded and interpreted by ab initio calculations. The population and dissociation of states belonging to the C and D Rydberg series in CO seem to explain the production of the observed triplet states but not the 3p 1D state.

    Neutral photodissociation of NO is reported in the 17-26 eV energy range. No known molecular states can account for the collected data. New information regarding the precursor states of the observed neutral dissociation is provided by ab initio calculations.

    Autoionization of superexcited states in molecular nitrogen is evidenced by strong deviations of the Franck-Condon ratio in the fluorescence of the N2+ B state. Ab initio calculations predict the existence of autoionizing-excited states that may account for some of the observed structures in the 20-46 eV energy range.

    Selective molecular fluorescence from the npó1Óu+ and npð 1Ðu (n=3-7) Rydberg levels to the E,F 1Óg+ state in H2 was recorded and rotationally analyzed. Vibrational levels of the E,F 1Óg+ state (vEF =0,1,3,6-10) are determined. The predissociation of npð 1Ð+ levels is observed in agreement with the literature.

    Fragmentation of SF6 was investigated after excitation with 25–80 eV photons. Dispersed fluorescence measurements reveal the emission of S, S+, F and F+ excited atoms. These fragments are produced after single, double and triple excitations as well as direct ionizations and shake-ups in SF6.

    Photoabsorption and fluorescence yield have been measured in SF5CF3 using 10-30eV photons. The photoabsorption spectrum can be explained in terms of its similarities to those of the SF6 and CF4 molecules. The dispersed and un-dispersed fluorescence resemble those of the CF3X family. Several features suggest the migration of an F atom across the S-C bond that fragments the molecule producing excited CF4.

    Doubly excited states of H2 have been investigated in the range of 26-60 eV by monitoring Balmer á emission. The experimental data show the already known emission correlated with the fragmentation of the Q1 and Q2 states, and new features which could be attributed to dissociative photoionization and higher lying doubly excited states Qn (n>2) of the hydrogen molecule

  • 14.
    Álvarez Ruiz, Jesús
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Erman, Peter
    KTH, Tidigare Institutioner, Fysik.
    Rachlew-Källne, Elisabeth
    KTH, Tidigare Institutioner, Fysik.
    Rius Riu, Jaume
    KTH, Tidigare Institutioner, Fysik.
    Stankiewicz, Marek
    KTH, Tidigare Institutioner, Fysik.
    Veseth, V.
    Neutral dissociation of superexcited states in carbon monoxide2002Inngår i: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 35, nr 13, s. 2975-2983Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Neutral photodissociation of CO has been investigated using synchrotron light in the range 19-26 eV by observing dispersed fluorescence from excited neutral C atoms. Follow-up ab initio calculations support the observed neutral carbon excitation functions, which to a large extent are associated with the CO Rydberg - series converging to the CO+ C and D states.

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