Diss. (sammanfattning) Linköping : Linköpings universitet, 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2007. / Härtill 9 uppsatser.

<p>Dissociative recombination is the process in which a molecular ion recombines with an electron and then fragments into neutral products. This process has been studied in many experiments over the years at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. In this thesis the experimental methods and data analysis procedures used to investigate dissociative recombination are presented together with the results for several diatomic and triatomic ions. Cross sections and branching fractions of the different breakup channels have been determined. An imaging system was introduced to study the fragmentation channels in detail. The main focus is on the dynamics of the three-body breakup of triatomic dihydride ions. This work includes the results from the dissociative recombination of NO⁺, SH₂⁺, SD₂⁺, PD₂⁺, NH₂⁺, CH₂⁺, H₂O⁺ and H₃⁺.</p>

Dissociative recombination is the process in which a molecular ion recombines with an electron and then fragments into neutral products. This process has been studied in many experiments over the years at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. In this thesis the experimental methods and data analysis procedures used to investigate dissociative recombination are presented together with the results for several diatomic and triatomic ions. Cross sections and branching fractions of the different breakup channels have been determined. An imaging system was introduced to study the fragmentation channels in detail. The main focus is on the dynamics of the three-body breakup of triatomic dihydride ions. This work includes the results from the dissociative recombination of NO+, SH2+, SD2+, PD2+, NH2+, CH2+, H2O+ and H3+.

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. / QC 20100910

<p>To further the understanding and knowledge about fusion plasmas and their behaviour during different conditions, it is important to be able to collect information about the plasma and the processes occurring within it. Visible spectroscopy, or the study of the visible wavelength light emitted by the plasma, is a useful tool in this search for knowledge.</p><p>This thesis is based on experiments where visible wavelength light has been measured and analysed in order to determine quantities about the emitting source. Doppler shift measurements of spectral lines have been utilised to determine the toroidal rotation velocities of plasma impurity ions and to study the correlation with mode rotation and the effect of active feedback control of the resistive wall modes. Information on the impurities present in the plasma has been determined and the calibrated intensities of spectral lines has yielded impurity concentrations, particle fluxes and electron temperature and densities. Ion temperatures have been determined from Doppler broadening measurements.</p><p>The measured vibrational and rotational band structure of deuterium molecular spectra has been analysed in order to calculate rotational and vibrational temperatures, relative populations and molecular particle fluxes. The effect of the molecular flux on simple calculations of atomic flux has also been studied. Specific molecular states and transitions of deuterium have also been probed with synchrotron radiation to study the level and transition energies.</p><p>The measurement and analysis of visible wavelength light has been demonstrated to be a sensitive diagnostic tool in the quest for increased knowledge about fusion plasmas and molecular structure.</p>

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 8 uppsatser. På titelsidan feltryck av serietitel: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology.

Diss. (sammanfattning) Uppsala : Uppsala universitet, 2007. / Härtill 8 uppsatser.

<p>Resonant states are multiply excited states in atoms and ions that have enough energy to decay by emitting an electron. The ability to emit an electron and the strong electron correlation (which is extra strong in negative ions) makes these states both interesting and challenging from a theoretical point of view. The main contribution in this thesis is a method, which combines the use of <i>B </i>splines and complex rotation, to solve the three-electron Schrödinger equation treating all three electrons equally. It is used to calculate doubly excited and triply excited states of ⁴<i>S</i> symmetry with even parity in He^-. For the doubly excited states there are experimental and theoretical data to compare with. For the triply excited states there is only theoretical data available and only for one of the resonances. The agreement is in general good. For the triply excited state there is a significant and interesting difference in the width between our calculation and another method. A cause for this deviation is suggested. The method is also used to find a resonant state of ⁴<i>S</i> symmetry with odd parity in H^2-. This state, in this extremely negative system, has been predicted by two earlier calculations but is highly controversial.</p><p>Several other studies presented here focus on two-electron systems. In one, the effect of the splitting of the degenerate H(<i>n=</i>2) thresholds in H^-, on the resonant states converging to this threshold, is studied. If a completely degenerate threshold is assumed an infinite series of states is expected to converge to the threshold. Here states of ¹<i>P</i> symmetry and odd parity are examined, and it is found that the relativistic and radiative splitting of the threshold causes the series to end after only three resonant states. Since the independent particle model completely fails for doubly excited states, several schemes of alternative quantum numbers have been suggested. We investigate the so called DESB (Doubly Excited Symmetry Basis) quantum numbers in several calculations. For the doubly excited states of He^-mentioned above we investigate one resonance and find that it cannot be assigned DESB quantum numbers unambiguously. We also investigate these quantum numbers for states of ¹<i>S </i>even parity in He. We find two types of mixing of DESB states in the doubly excited states calculated. We also show that the amount of mixing of DESB quantum numbers can be inferred from the value of the cosine of the inter-electronic angle. In a study on Li^-the calculated cosine values are used to identify doubly excited states measured in a photodetachment experiment. In particular a resonant state that violates a propensity rule is found.</p>

Resonant states are multiply excited states in atoms and ions that have enough energy to decay by emitting an electron. The ability to emit an electron and the strong electron correlation (which is extra strong in negative ions) makes these states both interesting and challenging from a theoretical point of view. The main contribution in this thesis is a method, which combines the use of B splines and complex rotation, to solve the three-electron Schrödinger equation treating all three electrons equally. It is used to calculate doubly excited and triply excited states of 4S symmetry with even parity in He-. For the doubly excited states there are experimental and theoretical data to compare with. For the triply excited states there is only theoretical data available and only for one of the resonances. The agreement is in general good. For the triply excited state there is a significant and interesting difference in the width between our calculation and another method. A cause for this deviation is suggested. The method is also used to find a resonant state of 4S symmetry with odd parity in H2-. This state, in this extremely negative system, has been predicted by two earlier calculations but is highly controversial. Several other studies presented here focus on two-electron systems. In one, the effect of the splitting of the degenerate H(n=2) thresholds in H-, on the resonant states converging to this threshold, is studied. If a completely degenerate threshold is assumed an infinite series of states is expected to converge to the threshold. Here states of 1P symmetry and odd parity are examined, and it is found that the relativistic and radiative splitting of the threshold causes the series to end after only three resonant states. Since the independent particle model completely fails for doubly excited states, several schemes of alternative quantum numbers have been suggested. We investigate the so called DESB (Doubly Excited Symmetry Basis) quantum numbers in several calculations. For the doubly excited states of He- mentioned above we investigate one resonance and find that it cannot be assigned DESB quantum numbers unambiguously. We also investigate these quantum numbers for states of 1S even parity in He. We find two types of mixing of DESB states in the doubly excited states calculated. We also show that the amount of mixing of DESB quantum numbers can be inferred from the value of the cosine of the inter-electronic angle. In a study on Li- the calculated cosine values are used to identify doubly excited states measured in a photodetachment experiment. In particular a resonant state that violates a propensity rule is found.