| 1. |
- Álvarez Ruiz, Jesús, et al.
(författare)
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Neutral dissociation of superexcited states in carbon monoxide
- 2002
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 35:13, s. 2975-2983
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Tidskriftsartikel (refereegranskat)abstract
- 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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| 2. |
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| 3. |
- Erman, P., et al.
(författare)
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Non Franck-Condon effects in photoionization of molecular oxygen
- 2000
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Ingår i: Physica scripta. T. - 0281-1847. ; 62:4, s. 294-300
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Tidskriftsartikel (refereegranskat)abstract
- We present a theoretical and experimental analysis of non Franck-Condon effects in photoionization to the b (4)Sigma(g)(-), state of O-2(+). Experimentally, by dispersing the synchrotron radiation induced O-2(+) b (4)Sigma(g)(-) a (IIu)-I-4 fluorescence we derive the b (4)Sigma(g)(-), State vibrational branching ratios in the excitation energy range 21-34 eV. The vibrational branching ratios reveal features in the region 21-28 eV indicating strong non Franck-Condon effects. The experimental results have been analysed by computing ab initio the vibrational population branching ratios using a many-body perturbation method. Additionally the autoionizing neutral states existing in this energy region have been studied. We have computed the energies of the valence states up to an energy of 30 eV their transition moments for excitations from the ground state, and autoionization rates. Our calculations show, that strong non Franck-Condon effects recorded in the branching ratio spectrum (below 25 eV) are actually caused by the narrow 3 sigma(g) --> sigma(u) shape resonance, and its coupling to the 1 pi(u) --> pi(g) channel.
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| 4. |
- García, Emilio Melero, et al.
(författare)
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Neutral dissociation of superexcited states in nitric oxide
- 2003
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Ingår i: Chemical Physics. - 0301-0104 .- 1873-4421. ; 293:1, s. 65-73
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 5. |
- Hedqvist, Anders, et al.
(författare)
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Contributions of thermal charge exchange excitation to the Rydberg series of Cl16
- 2000
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 33:3, s. 375-382
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Tidskriftsartikel (refereegranskat)abstract
- Spectra from the Rydberg series 1s-np for the principal quantum numbers n greater than or equal to 8 of Cl16+ are observed on the JET tokamak. Individual lines up to n = 15 are resolved. The line intensity of n = 10 is enhanced, relative to the underlying 1/n(3) scaling, due to charge exchange collisions with neutral deuterium in the ground state. The observations are compared with predictions based on available partial charge exchange cross section data. There is generally good agreement, however, some details of the predicted n-shell distribution are different from those observed in the experiment.
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| 6. |
- Horvath, Akos, et al.
(författare)
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Nuclear power in the 21st century : Challenges and possibilities
- 2016
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Ingår i: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 45:Suppl. 1, s. 38-49
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Forskningsöversikt (refereegranskat)abstract
- The current situation and possible future developments for nuclear power—including fission and fusion processes—is presented. The fission nuclear power continues to be an essential part of the low-carbon electricity generation in the world for decades to come.There are breakthrough possibilities in the development of new generation nuclear reactors where the life-time of the nuclear waste can be reduced to some hundreds of years instead of the present time-scales of hundred thousand of years. Research on the fourth generation reactors is needed for the realisation of this development. For the fast nuclear reactors, a substantial research and development effort is required in many fields—from material sciences to safety demonstration—to attain the envisaged goals. Fusion provides a long-term vision for an efficient energy production. The fusion option for a nuclear reactor for efficient production of electricity has been set out in a focussed European programme including the international project of ITER after which a fusion electricity DEMO reactor is envisaged.
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| 7. |
- Jakubowska, Katarzyna
(författare)
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Development of visible spectroscopic techniques for applications in plasma diagnostics
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis visible spectroscopy is developed and used for two applications. Studies of motional Stark effect spectra for diagnosing the current distribution in the fusion plasmas with two different spectroscopic diagnostic systems: ratiometry and interferometry. Both systems provide non-invasive method for diagnosis of the internal plasma properties, e.g. magnetic field. Pitch angle of magnetic field lines are obtained from polarisation of Stark split Hα spectral lines emitted by energetic hydrogen atoms injected into the plasma volume by neutral beam. Several methods of calibration of the systems on TEXTOR and JET are discussed. The main result of this work is the first measurement of the safety factor radial profile with new ratiometric MSE system on TEXTOR. Studies of molecular fragmentation of free molecules CH4 and NH3 excited with synchrotron radiation by detection of the fluorescence from the fragments. The results give the decay path ways for the molecules when excited below the N and C ionisation edges.
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| 8. |
- Karawajczyk, A., et al.
(författare)
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Neutral fragmentation of superexcited oxygen molecules
- 2000
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 61:3, s. art. no.-32718
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of neutral dissociation of oxygen molecules in the excitation energy range 15-25 eV have been studied in a dispersed fluorescence experiment. By detecting the fluorescence from excited oxygen atoms, we find that neutral superexcited O-2 states below 20 eV dissociate into O(g.s.) + O(3s,3p). At higher excitation energies (h nu = 20-25 eV) the curve-crossing interactions following excitations to members of the Rydberg c (4)Sigma(u)(-) series also yield atoms in Rydberg states (nl,n greater than or equal to 4). The experimental data are analyzed on the ground of many-body perturbation theory, calculations which indicate the structure of the predissociating states converging to the experimentally observed ones.
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| 9. |
- Kuldkepp, Mattias, 1976-
(författare)
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Diagnostics for advanced fusion plasma scenarios
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Over the past decade, fusion research has showed the potential of being a main candidate for energy production for future generations. Further advances in improved fusion performance are therefore vital. This thesis focuses on advanced fusion plasma scenarios and their diagnostic requirements. In particular the design of a motional Stark effect (MSE) diagnostic at the MAST spherical tokamak and the analysis of magneto-hydrodynamic mode feedback control and pulsed poloidal current drive (PPCD) at the reversed field pinch (RFP) experiment EXTRAP T2R are discussed. The MSE diagnostic is important for the determination of the plasma current profile, information that is necessary for studies in advanced confinement scenarios like reversed shear profiles or current holes. The MAST MSE system has two channels and selects the spectral components using 1Å FWHM interference filters. The diagnostic has been commissioned during the fall of 2006 and the results show the feasibility of the technique with rms-noise ~0.5° using a time resolution of 1 ms. Investigations of mirror labyrinths for the future ITER MSE diagnostic highlight the need for careful calibration considerations. Feedback control and PPCD are techniques for improved confinement. Feedback control dramatically decreases impurity influx at the end of discharges while transport in the bulk plasma is largely unaffected. During PPCD the transport is seen to decrease and it is demonstrated that PPCD and feedback control can be employed simultaneously. New and innovative techniques for fusion spectroscopy are furthermore described. This includes the use of correlations in line integrated signals to determine ion emission profiles in poloidally symmetric environments. Good agreement with other diagnostic methods is obtained. The assessment of electron temperature profiles using measured differences between Thomson scattering and vacuum ultra-violet spectroscopy is also shown.
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| 10. |
- Melero Garcia, Emilio, 1978-
(författare)
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Synchrotron radiation spectroscopy of molecular dynamics beyond the valence shell
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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