No abstract provided. / Thesis / Doctor of Philosophy (PhD) / Scope and contents: The atomic vibrations in rubidium have been studied by the method of slow neutron spectrometry. The results have been analysed to yield atomic force constants which are used to compute the phonon frequency distribution. An interesting effect in the [00ζ]L branch has been examined, and an explanation of the observations is offered. Anharmonic calculations of frequency shifts and widths are presented, as well as a calculation of the anharmonic heat capacity. The third and fourth derivatives of the real space interatomic potential, which are required for these computations, are estimated in various ways. A determination of the lattice spacing of rubidium by neutron diffraction is described.

This work describes a study of the gamma rays and beta particles emitted during the decay of the 33-second fission product Krypton-90. Procedures for the analysis of gamma, gamma-gamma coincidence, beta and beta-gamma coincidence experiments are discussed. The application of these analyses to the short-lived Krypton-90 activity yields the prominent features of this decay. The total energy release of this decay was found to be 4.56 ± 0.02MeV, in agreement with beta systematics. A level scheme for the daughter, Rubidium-90, is proposed. / Thesis / Doctor of Philosophy (PhD)

In this thesis we numerically compute the scattering lengths and bound states for sodium-rubidium collisions at low energy. This work was motivated by experiments which aim to produce Bose-Einstein condensates (BEC) mixtures of sodium-rubidium. Elastic collision properties are important for the rethermalization of the atoms during the evaporative cooling process. Inelastic processes, which we also discuss to some extent, cause trap losses in those experiments. In order to reach the required temperature and density the elastic collision rates should be sufficiently large compared to the inelastic rates. The scattering lengths, which completely specify the elastic collision parameters at low energy, determine the miscibility and phase diagram of the sodium-rubidium condensate mixture. We calculate the scattering lengths approximately and find agreement with previous calculations indicating that miscible phases of sodium and rubidium condensates do not appear to be feasible in the absence of external fields.

Atominterferometrie (AI) auf Basis von Lichtpulsen ist ein wichtiges Werkzeug der Präzisionsmesstechnik in Bereichen der inertialen Sensorik oder Fundamentalphysik geworden. Vor allem in Kombination mit ultrakalten, atomaren Quellen, sowie der Verwendung im schwerelosen Raum, werden hohe Sensitivitäten erwartet, die Verletzungen des schwachen Äquivalenzprinzips nachweisen können. QUANTUS-2 ist ein mobiles Atominterferometer, das am ZARM Fallturm in Bremen operiert. Durch seine Atomchip-basierte atomare Rubidiumquelle mit hoher Flussdichte dient es als Vorreiterexperiment für zukünftige Weltraummissionen, bei denen Schlüsseltechnologien wie die Erzeugung von Bose-Einstein Kondensaten (BECs), Delta-Kick Kollimation oder Anwendung verschiedener AI-Geometrien auf sekundenlangen Zeitskalen untersucht werden. Im Rahmen dieser Arbeit wurde ein Kalium-Diodenlasersystem aufgebaut, um die Funktionalität auf Zwei-Spezies Nutzung zu erweitern. Basierend auf dem Design des Rubidium-Diodenlasersystem mit mikrointegrierten Laserdiodenmodulen und kompakter Elektronik, konnte es erfolgreich qualifiziert werden. In einem Machbarkeitsbeweis wurde eine magneto-optische Falle mit Kalium generiert, die die Fähigkeit des Lasersystems zum Fangen von Atomen demonstriert. Mit Rubidium wurden offene Ramsey-Interferometer und Mach-Zehnder Interferometer (MZIs) am Boden und in über 155 Abwürfen untersucht. Die Kombination von unterschiedlich stark Delta-Kick kollimierten BECs und AI in Schwerelosigkeit eröffnete eine neue Methode zur Bestimmung der magnetischen Linsendauer zur optimalen Kollimierung. Asymmetrische MZIs mit Interferometerzeiten von 2T > 1s konnten erfolgreich demonstriert werden. Mit gravimetrischen Untersuchungen am Boden auf Basis von MZIs und einer zusätzlichen Methode der Atomlevitation wurde die lokale Gravitationsbeschleunigung g ermittelt. Die untersuchten Schlüsseltechnologien sind fundamentale Notwendigkeiten, um den Weg für zukünftige Weltraummissionen aufzubereiten. / Light-pulse atom interferometry (AI) is an important tool for high precision measurements in the fields of inertial sensing or fundamental physics. Especially in combination with ultra-cold atomic sources and operation in microgravity, high sensitivities are expected that are necessary for the search for violations of the weak equivalence principle. QUANTUS-2 is a mobile atom interferometer operating at the ZARM drop tower in Bremen. With its high-flux, atom chip-based atomic rubidium source, it serves as a pathfinder for future space missions, examining key technologies like the generation of Bose-Einstein condensates (BECs), implementation of delta-kick collimation or application of various AI geometries. In this thesis, a potassium diode laser system has been built to complete the preordained functionality of dual-species operation. Based on the design of the rubidium laser system with micro-integrated laser diode modules and compact electronics, it successfully passed the qualification tests. In a proof of principle measurement, a potassium magneto-optical trap could be generated to prove the system’s capability of trapping atoms. With rubidium, open Ramsey type interferometers and Mach-Zehnder interferometers (MZIs) were examined on ground and in over 155 drops in microgravity. The combination of variably delta-kicked collimated BECs and AI in microgravity revealed a new technique to determine the magnetic lens duration for optimal collimation. Asymmetric MZIs with interferometry times of 2T > 1s have successfully been demonstrated. Gravimetric examinations on ground with MZIs and by an additional levitation technique have been performed to determine the local gravitational acceleration g. The examined key technologies are fundamental necessities that have to be considered to pave the way for future space missions.

Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: A magneto optical trap (MOT) is capable of trapping a vapor cloud consisting of atoms cooled down to the micro Kelvin range. Three orthogonal pairs of counter-propagating laser beams of the correct circular polarisation form an optical molasses which facilitates the cooling of neutral atoms. Additionally a spatially non-uniform magnetic field produced by two current carrying coils in a Maxwell gradient configuration is used to trap the cooled atoms. In this report the effects of the trap parameters, including the laser beam intensity and frequency detuning, beam diameter and magnetic field gradient, on the number of trapped atoms are discussed. Secondly the development of an experimental setup for laser cooling and trapping of 87Rb atoms in vacuum with the aid of a MOT is presented. All trap components were implemented and characterised. The vacuum system and trapping chamber in which the cooling takes place were designed and constructed. A rubidium getter to act as a source of atoms was integrated into the vacuum system. The two external cavity diode lasers used for trapping and optical re-pumping were characterised. The optical setup required for the optical molasses was designed, constructed and characterised. Saturated absorption spectroscopy was performed to investigate the hyperfine structure of 87Rb and to frequency lock the lasers. We report on the current status of the project with regards to progress, results and future work. / AFRIKAANSE OPSOMMING: 'n Magneto-optiese val (magneto optical trap, MOT) kan 'n dampwolk van atome vang en afkoel tot in die mikro Kelvin bereik. Drie ortogonale pare laserbundels, elke paar voortplantend in teenoorgestelde rigtings, met die korrekte sirkelvormige polarisasie vorm 'n sogenaamde optiese molasse wat die afkoeling van neutrale atome moontlik maak. Bykomend word 'n ruimtelik nie-uniforme magneetveld geproduseer deur twee stroomdraende spoele in 'n Maxwell gradient-opstelling gebruik om die afgekoelde atome te vang. In hierdie verslag word die invloed van die val parameters, insluitend die laserbundel intensiteit en frekwensie afstemming, die laserbundel deursnit en magneetveld gradiënt, op die aantal atome in die val bespreek. Tweedens word die ontwikkeling van 'n eksperimentele opstelling vir laser afkoeling en vang van 87Rb atome in vakuum met die hulp van 'n MOT voorgelê. Alle komponente van die val is geïmplementeer en gekarakteriseer. Die vakuumsisteem en val-kamer waarin die afkoeling plaasvind is ontwerp en gebou. 'n Rubidium gasbinder is in die vakuumsisteem ingebou om as 'n bron van atome te dien. Die twee eksterne resonator diodelasers wat gebruik is vir die val en die optiese terugpomp is gekarakteriseer. Die optiese opstelling wat nodig is vir die optiese molasse is ontwerp, gebou en gekarakteriseer. Versadigde absorpsiespektroskopie is uitgevoer om die hiperfynstruktuur van 87Rb te ondersoek en om die lasers se frekwensies te stabiliseer. Verslag word gedoen oor die huidige stand van die projek wat betref vordering, resultate en toekomstige werk.

No description available.

This thesis set out to investigate light storage based on dynamic electromagnetically induced transparency (EIT) in a room-temperature atomic ensemble of rubidium as a means to provide a quantum memory for single-photons created by a single rubidium atom coupled to a high-finesse optical resonator. Setting up the light storage medium presented a new addition to the research group's portfolio of experimental techniques and led to investigations of EIT, slow light and stored light in warm rubidium-87 vapour. Lambda level schemes connecting Zeeman or hyperfine substates on the D₁ and D₂ lines were addressed in rubidium vapour cells containing different buffer gases and different isotopic fractions of rubidium-87 and rubidium-85. Single beam spectroscopy with a weak probe was used to characterise the vapour cells. A numerical method to fit the D line spectrum to a theoretical model to include isotopic fractions and collisional broadening of a buffer gas has been implemented. Temperature and isotopic fractions could be reliably extracted from the fit parameters. For an offset-stabilisation of two lasers to address a lambda level scheme connecting the two different hyperfine groundstates in rubidium a phase locked loop including a frequency divider has been designed and implemented. Light storage and retrieval has been demonstrated using a Zeeman scheme on the D1 line. Two microsecond long classical light pulses containing one million photons on average were stored and retrieved with an efficiency of 15% after a delay of one microsecond. Several methods of attenuating the strong co-propagating control laser beam to allow for lowering the signal pulse intensity in future experiments are discussed.

O potássio (K) é o segundo nutriente mais requerido pelo milho. Os produtores de milho em sistema de plantio direto (SPD) antecipam na aveia a dose de K que seria aplicada no milho. O uso da adubação antecipada se deve a redução de custo da semeadura, e a possibilidade de instalar a cultura de acordo com o zoneamento agroclimático. Esta pesquisa foi realizada com o objetivo de avaliar a eficiência de uso do K proveniente do fertilizante, por meio do marcador rubídio (85Rb), em razão dos sistemas de adubação potássica na rotação aveia-milho. Os experimentos foram realizados em Guarapuava-PR e Taquarituba-SP, entre abril de 2012 e abril de 2013, em solos com alto teor de K. A eficiência de uso do K proveniente do fertilizante foi determinada nos seguintes sistemas de adubação: K no perfilhamento da aveia; K em pré-semeadura do milho; K na semeadura do milho; K em cobertura no estádio V3; e K em cobertura nos estádios V3 (50%) e V6 (50%). Os sistemas de adubação foram casualizados em quatro blocos, nos dois experimentos. A maior eficiência de uso do K foi obtida no sistema de adubação em pré-semeadura do milho, entre 15 e 30 dias, sem prejuízo da produtividade. / Potassium (K) is the second most required nutrient for corn. Farmers that grow corn in no-tillage system (NTS) have been anticipated on oats crop the K fertilizer amount that should be applied in corn crop. The adoption of early fertilization system is related to cost reduction and the possibility of the main crop establishment in the period recommended by the agroclimatic zoning. This research aims to evaluate the K use efficiency from the fertilizer with the tracer Rubidium (85Rb), according to potassium fertilization systems in oat-corn rotation. The experiments were conducted in Guarapuava-PR and Taquarituba-SP between April 2012 and April 2013, in soils with high content of K. Potassium use efficiency from the fertilizer was determined in the following fertilization systems: K on oat tillering, K in corn pre-sowing, K in corn sowing, K topdressing in stage V3, and K topdressing in stages V3 (50%) and V6 (50%). The fertilization systems were randomized into four blocks, in both experiments. The system of K fertilization was applied pre-sowing corn, between 15 and 30 days, was more efficient in the use of K from the fertilizer without damaging productivity.

O potássio (K) é o segundo nutriente mais requerido pelo milho. Os produtores de milho em sistema de plantio direto (SPD) antecipam na aveia a dose de K que seria aplicada no milho. O uso da adubação antecipada se deve a redução de custo da semeadura, e a possibilidade de instalar a cultura de acordo com o zoneamento agroclimático. Esta pesquisa foi realizada com o objetivo de avaliar a eficiência de uso do K proveniente do fertilizante, por meio do marcador rubídio (85Rb), em razão dos sistemas de adubação potássica na rotação aveia-milho. Os experimentos foram realizados em Guarapuava-PR e Taquarituba-SP, entre abril de 2012 e abril de 2013, em solos com alto teor de K. A eficiência de uso do K proveniente do fertilizante foi determinada nos seguintes sistemas de adubação: K no perfilhamento da aveia; K em pré-semeadura do milho; K na semeadura do milho; K em cobertura no estádio V3; e K em cobertura nos estádios V3 (50%) e V6 (50%). Os sistemas de adubação foram casualizados em quatro blocos, nos dois experimentos. A maior eficiência de uso do K foi obtida no sistema de adubação em pré-semeadura do milho, entre 15 e 30 dias, sem prejuízo da produtividade. / Potassium (K) is the second most required nutrient for corn. Farmers that grow corn in no-tillage system (NTS) have been anticipated on oats crop the K fertilizer amount that should be applied in corn crop. The adoption of early fertilization system is related to cost reduction and the possibility of the main crop establishment in the period recommended by the agroclimatic zoning. This research aims to evaluate the K use efficiency from the fertilizer with the tracer Rubidium (85Rb), according to potassium fertilization systems in oat-corn rotation. The experiments were conducted in Guarapuava-PR and Taquarituba-SP between April 2012 and April 2013, in soils with high content of K. Potassium use efficiency from the fertilizer was determined in the following fertilization systems: K on oat tillering, K in corn pre-sowing, K in corn sowing, K topdressing in stage V3, and K topdressing in stages V3 (50%) and V6 (50%). The fertilization systems were randomized into four blocks, in both experiments. The system of K fertilization was applied pre-sowing corn, between 15 and 30 days, was more efficient in the use of K from the fertilizer without damaging productivity.

In this thesis we study light-matter coherence phenomena related to the interaction of a coherent laser field and the so-called Λ-system, a three-level quantum system (e.g., an atom). We observe electromagnetically induced transparency (EIT), slow and stored light in hot rubidium vapor. For example, a 6 μs Gaussian pulse propagate at a velocity of ~1 km/s (to be compared with the normal velocity of 300 000 km/s). Dynamic changes of the control parameter allows us to slow down a pulse to a complete stop, store it for ~100 μs, and then release it. During the storage time, and also during the release process, some properties of the light pulse can be changed, e.g., frequency chirping of the pulse is obtained by means of Zeeman shifting the energy levels of the Λ-system. If, bichromatic continuous light fields are applied we observe overtone generation in the beating signal, and a narrow `dip' in overtone generation efficiency on two-photon resonance, narrower than the `coherent population trapping' transparency. The observed light-matter coherence phenomena are explained theoretically from first principles, using the Lindblad master equation, in conjunction with the Maxwell's equations. Furthermore, we analyze an optical delay-line based on EIT and show that there is in principle (besides decoherence) no fundamental limitation, but the usefulness today is scant. The combination of EIT and a photonic crystal cavity is inquired into, and we show that the quality value of a small resonator (area of 2.5λ×2.5λ with a missing central rod) can be enhanced by a factor of 500 due to the increased modal density close to two-photon resonance. Open system effects (decoherence effects) are thoroughly investigated using a coherence vector formalism, furthermore, a vector form of the Lindblad equation is derived. Specifically we find an open system channel that lead to slow light and gain. / QC 20100812