Thesis--University of California, Berkeley, 1962. / "UC-34 Physics" -t.p. "TID-4500 (17th Ed.)" -t.p. Includes bibliographical references (p. 135-139).

It was the purpose of this investigation to study the hyperfine structure of the β-unstable isotopes of samarium using the atomic beam magnetic resonance technique. A brief review is given of the nuclear and atomic theory necessary for the interpretation of the experiments. The hyperfine interaction constants (Mc/sec) for Sm153, and the nuclear moments inferred from them, are summarized below: A1 = - 2.100(5) B1 = 289.042(4) A2 = - 2.573(6) B2 = 306.521(21) C2 = - 0.0003(9) A3 = - 3.115(4) B3 = 165.824(20) C3 = - 0.0087(12) μI = - 0.021(1) n.m. Q = 1.1(3) barns From the quadrupole moment it follows that the nuclear deformation δ = 0.25(5). The magnetic moment disagrees with the predictions of the Nilsson model for either spin 3/2 state with which the Sm153 ground state might be associated. Also determined was the spin of Sm155. The result, I = 3/2, confirms the assignment from the less direct evidence available from radioactive decay studies. The more extensive measurements necessary to determine the moments were not attempted. / Thesis / Doctor of Philosophy (PhD)

No description available.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 1975 / Vita. / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Physics

<p>An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects.</p><p>This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings.</p><p>A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negative ions. Results of lifetime measurements are reported and the techniques and methods used are described.</p><p>Another weak effect is hyperfine interaction, which splits the energy levels of an atom or ion. Hyperfine splitting is very small and usually special spectral techniques are needed to resolve such structure. A laser can, in combination with an electromagnetic radio-frequency field, be used for accurate determination of hyperfine structures in atomic ions. Such measurements are also important for evaluation of astrophysical properties, since hyperfine structure can broaden the spectral lines. An experimental setup for such double resonance measurements has been developed and constructed. Results of experimental measurements are reported and the technique is described.</p>

No description available.

No description available.

Les moments magnétiques peuvent donner des détails sur la structure nucléaire et sur la composition de la fonction d'onde du noyau, tout spécialement si le caractère de particule indépendante du noyau est prépondérant. Pour cette raison, le moment magnétique du premier état excité du noyau radioactif riche en neutrons 72Zn a été mesuré au Grand Accélérateur National d'Ions Lourds (GANIL, Caen, France). Le résultat de l'expérience a confirmé les prédictions du modèle en couches, même si l'incertitude sur la mesure ne pouvait pas contraindre fortement les modèles. La mesure a été effectuée en utilisant la technique du champ transitoire (TF) et les noyaux d'intérêt ont été produits par fragmentation. Avant cette expérience, la technique TF à haute vitesse n'avait été utilisée qu'avec des projectiles allant jusqu'à Z=24. Ce fut donc la première fois qu'un moment magnétique d'un ion lourd avec Z >24 avait été mesurée à cette vitesse. Afin de développer la technique et de recueillir des informations sur l'interaction hyperfine qui agit entre les électrons et les noyaux polarisés, deux expériences ont été menées au Laboratorio Nationale del Sud (LNS, Catane, Italie). Dans cette thèse, je présenterai le développement de la technique TF à haute vitesse pour les expériences g(2+;72 Zn) et BTF (Kr, Ge). L'analyse des résultats et leur interprétation seront ensuite discutées.

An atom or ion can change quantum state, usually through emission or absorption of a photon. The photon has the same energy as the energy difference between the states of the transition. The states, or energy levels, of an atom are quantized and light emitted, or absorbed, from the atom is therefore of specific wavelengths, giving spectral lines. The spectrum of an atomic ion is unique and contains information of the structure and energy levels of the ion. The spectrum of an atom can be used as a fingerprint in determinations of the abundance of the element in different objects. This thesis is focused on some weak effects observed by spectroscopy. Although the effects are weak, they turn out to be of great importance. According to quantum mechanics transitions between certain states are not allowed. Here the weak effects open the possibility for transitions. Spectral lines from forbidden transitions are very weak and difficult to observe under ordinary laboratorial conditions, but they are commonly observed from astrophysical objects and can be very useful for diagnostics of astrophysical plasmas. The first reported observation of forbidden lines was from an astrophysical object and at that time supposed to be from new, previous unknown, elements. If all possible decay channels from an energy level are forbidden, the energy level is metastable and has usually a lifetime 10$^8$ times longer than an ordinary excited state. Measurements of such long lifetimes are difficult since the ion need to be confined during the observation time. Confinement of ions can be achieved with a storage device, such as a storage ring or a trap, where the ions are stored without interacting with each other or the surroundings. A laser probing technique has been developed at the storage ring CRYRING, for measurements of lifetimes of metastable states. The technique has now been improved for measurement of longer lifetimes. The technique has also been modified to fit when measuring on negative ions. Results of lifetime measurements are reported and the techniques and methods used are described. Another weak effect is hyperfine interaction, which splits the energy levels of an atom or ion. Hyperfine splitting is very small and usually special spectral techniques are needed to resolve such structure. A laser can, in combination with an electromagnetic radio-frequency field, be used for accurate determination of hyperfine structures in atomic ions. Such measurements are also important for evaluation of astrophysical properties, since hyperfine structure can broaden the spectral lines. An experimental setup for such double resonance measurements has been developed and constructed. Results of experimental measurements are reported and the technique is described.

This paper treats a non-intrusive method of measuring electric fields in plasmas and other sensitive or hostile environments. The method is based on the use of an atomic hydrogen beam prepared in the metastable fine structure quantum state 2s1/2. Interaction with the field that is to be measured causes Stark mixing with the closely lying 2p1/2, whose spontaneous decay rate is much higher than that of 2s1/2. As a result, the total transition rate to the ground state and consequently the intensity of the Lyman-α line (121.6nm) is increased. Observations of emitted radiation from a region in which the interaction takes place are used to draw conclusions about the electric field, effectively providing a way to measure it. In the first section, the theory behind the method is described, using time dependent perturbation theory and taking into account both Lamb shift and hyperfine structure. A description of the set-up that we have used to test the theoretical predictions follows and practical aspects related to the operation of the experiment are briefly addressed. Measurements of the dependence of the Lyman-α intensity on both electric field frequency and amplitude are presented and shown to be in agreement with theory. These measurements have been performed in vacuum and in an argon plasma, both for static and RF fields. Two mechanisms, labeled oscillatory and geometrical saturation, that decrease the emitted intensity for strong fields are identified and described, and both are of importance for the future implementation of the studied diagnostic in a fusion device or other plasma experiment. Studies of the field profiles between a pair of electrically polarized plates have been carried out and algorithms for relating measured data to actual values of electric field strength have been developed. For static fields in vacuum, collected data is compensated for geometrical saturation and the resulting profiles are compared to those calculated with a finite element method. Good correspondence is seen in many cases, and where it is not, the discrepancies are explained. Static profile measurements in a plasma show the formation of a sheath whose thickness has been studied while varying discharge current, pressure and plasma frequency. The qualitative dependence of the sheath thickness on these parameters is in accordance with well established theory. When it comes to RF fields, a possible standing wave pattern is detected in the plasma despite problems with low signal to noise ratio. In order to optimize the working conditions of the set-up, effects of charge accumulation due to ions present in the hydrogen beam have been studied as well as errors due to residual particle fluxes during the off-phase when pulsing the beam. A conceptual design suggestion for implementing the method in the edge plasma of a tokamak or another similar device, based on the collected information, is also given.