The Layers of Meteoric Nickel and Aluminium in the Earth's Upper Atmosphere

The major source of metals in the upper atmosphere is the ablation of the roughly 28 tonnes of interplanetary dust that enters each day from space. This gives rise to the layers of metal atoms and ions that occur globally in the upper mesosphere/lower thermosphere (MLT) region between about 70 and 110 km. Metal species in the upper atmosphere offer a unique way of observing this region and of testing the accuracy of climate models in this domain. The overarching objective of this project will be to explore the MLT chemistry of two elements - Ni and Al. Specific objectives of the thesis will include conducting a laboratory study of the reaction kinetics of Ni and Al species, both neutral and ionized, that are relevant to understanding and modelling the contrasting chemistry of these elements in the MLT; extend lidar observations of the recently discovered Ni layer, which appears to be significantly broader than the well-known Na and Fe layers, with a Ni density that is roughly an order of magnitude higher than expected; attempt the first lidar observations of the AlO layer in the upper atmosphere where if successful, would be the first time that a molecular metallic species had been observed in the atmosphere; and develop the first global models of Ni by inserting the chemistry and the Meteoric Input Function (MIF) of Ni into a whole atmosphere chemistry-climate model and validating the resulting model simulations against lidar and rocket-borne mass spectrometric data of metallic ions

Experimental setup for fast BEC generation and number-stabilized atomic ensembles

Ultracold atomic ensembles represent a cornerstone of today’s modern quantum experiments. In particular, the generation of Bose-Einstein condensates (BECs) has paved the way for a myriad of fundamental research topics as well as novel experimental concepts and related applications. As coherent matter waves, BECs promise to be a valuable resource for atom interferometry that allows for high-precision sensing of gravitational fields or inertial moments as accelerations and rotations. In general, the sensitivity of state-of-the-art atom interferometers is fundamentally restricted by the Standard Quantum Limit (SQL). Multi-particle entangled states (e.g. spin-squeezed states, Twin-Fock states, Schrödinger cat states) generated in BECs can be employed to surpass the SQL and shift the sensitivity limit further towards the more fundamental Heisenberg Limit (HL). However, in current real-world atom interferometric applications, ultracold but uncondensed atomic clouds are employed, due to their speed advantage in the sample preparation. The creation of a BEC can take up several tens of seconds, while standard high-precision atom interferometers operate with a cycle rate of several Hz. In addition, the pursued entangled states can be only beneficial if technical noise sources, such as magnetic field or detection noise are not dominating the measurement resolution. These challenges need to be overcome in order to fully exploit the potential sensitivity gain offered by a quantum-enhanced atom interferometer. This thesis describes the design and implementation of a new experimental setup for Heisenberg-limited atom interferometry, which incorporates a high-flux BEC source and the manipulation and detection of atoms at the single-particle level. The presented fast BEC preparation includes a high-flux atom source in a double magneto-optical trap (MOT) configuration that allows to collect 87Rb atoms in a 3D-MOT, which is supplied by a 2D+-MOT with 2×10^10 atoms/s. Forced evaporative cooling of the atoms is divided into two stages, which is sequentially carried out in a magnetic quadrupole trap (QPT) and a crossed-beam optical dipole trap (cODT). The high-flux atom source together with the hybrid evaporation scheme allows to consistently produce BECs with an average of 2×10^5 atoms within 3.5 s. The capabilities of the single-particle resolving detection are demonstrated by realizing a feedback control loop to stabilize the captured number of atoms in a small MOT. A proof-of-principle measurement is demonstrated for the successful stabilization of a target number of 7 atoms with sub-Poissonian fluctuations. The number noise is suppressed by 18 dB below shot noise, which corresponds to a preparation fidelity of 92%. Based on this success, the thesis presents an even improved single-particle resolution. The system comprises a six-channel fiber-based optical setup, which provides independent intensity stabilization and frequency detuning, improved pointing stability as well as a better spatial overlap of the MOT beams. The presented high-speed BEC production combined with accurate atom number preparation and detection, as the two main features of the experimental apparatus, pave the way for a future entanglement-enhanced performance of atom interferometers

Vacuum ultraviolet photochemistry: I. Unimolecular decomposition studies of small hydrocarbon clusters by molecular beam photoionization mass spectrometry; II. Photofragment dynamics study of carbon disulfide by high resolution molecular beam laser photofragment time-of-flight mass spectrometry

The energetic and dissociation dynamics of (C(,2)H(,4))(,2)(\u27+), (C(,2)H(,4))(,3)(\u27+), (C(,3)H(,6))(,2)(\u27+) and (c-C(,3)H(,6))(,2)(\u27+) complexes have been studied by photoionization of neutral van der Waals ethylene dimers and trimers, propylene dimers and cyclopropane dimers. Photoionization efficiency studies of C(,2)H(,4), C(,3)H(,6) and c-C(,3)H(,6) and their clusters yield the ionization energies of (C(,2)H(,4))(,n=1,2,3), (C(,3)H(,6))(,n=1,2) and (c-C(,3)H(,6))(,n=1,2) and the appearance energies of C(,3)H(,5)(\u27+) and C(,4)H(,7)(\u27+) from (C(,2)H(,4))(,2). With the estimated values of (C(,2)H(,4))(,n=2,3,4), (C(,3)H(,6))(,2) and (c-C(,3)H(,6))(,2), the bond dissociation energies of (C(,2)H(,4))(,n=1,2,3)(\u27+) C(,2)H(,4), C(,3)H(,6)(\u27+) C(,3)H(,6) and c-C(,3)H(,6)(\u27+) c-C(,3)H(,6) are deduced. It is concluded that the (C(,2)H(,4))(,3)(\u27+), (C(,3)H(,6))(,2)(\u27+) and (c-C(,3)H(,6))(,2)(\u27+) loose complexes arrange to the common C(,6)H12+ collision complexes prior to fragmentation by comparing the major product channels in the unimolecular decompositions of these species. A new molecular beam laser photofragment time-of-flight mass spectrometer with rotatable beam source and movable detector has been constructed for studying photofragmentation dynamics of polyatomic molecules. The design considerations detailed assembly, and initial tests of this machine are described. The time-of-flight data of carbon disulfide laser photofragmentation at 193 nm have been taken at various beam source angles and fragment flight path lengths. The results give insight into the dynamics of the photofragmentation process;*USDOE Report IS-T-1260. This work was performed under Contract No. W-7405-Eng-82 with the U.S. Department of Energy

Cold Collisions of Ultracold Atoms

This thesis describes experiments investigating the collisions of alkali metal atoms at energies between 10 - 2000 uK, measured in units of the Boltzmann constant. The atoms are accelerated towards each other using a purpose-built collider comprised of a crossed-beam optical dipole trap, which enables us to collide dense ensembles of ultracold atoms in any internal state at relatively high energies. I present the results of two experiments centered around resonant enhancement of the collisions. The first is between homonuclear 40K atoms near a shape resonance where the fermionic nature of the atoms determines the character of multiple scattering effects. The second experiment involves heteronuclear 40K87Rb collisions near a magnetically-tunable Feshbach resonance where we measure parameters describing the resonance as a function of collision energy. Theoretical models are developed that let us describe the collisions using published empirical interaction potentials, and we find good agreement between these models and the experiment

Developments in nuclear microprobe analysis the measurement of the spatial distribution of stable isotope tracers

The potential of the nuclear microprobe for the determination of spatial distributions of stable isotope tracers has been examined. In a preliminary study the sensitivity of the isotope selective modes of operation of the microprobe (backscattering and nuclear reaction analysis) for the measurement of stable isotopes was examined using Mg, Si, Ni and Co as examples. The use of backscattering analysis coupled with high resolution detectors and heavy ion beams was assessed using Mg, Si, Ni and Ag as examples and found to be of limited application for stable isotope tracer studies. [Continues.

Nutrigenomic and methodologic reflections on metabolomics

Wissenschaftlich betrachtet befinden wir uns gerade inmitten der Erforschung der jungen OMICS‐Wissenschaften, was aus ernährungstechnischer Sicht die Chance birgt, möglicherweise in Zukunft optimierte Ernährungsempfehlungen ‐ abgestimmt auf das jeweilige Individuum‐ anbieten zu können. Diese Arbeit beschäftigt sich mit der aufsehenerregenden Thematik der Nutrigenomik, welche die Wechselwirkungen zwischen Nahrungsbestandteilen und deren Einflußnahme auf die Genexpression untersucht. Der Schwerpunkt ist auf die Disziplin der Metabolomik gesetzt, die als Bestandteil der OMICS‐Kaskade mit der Erforschung des gesamten Metaboloms betraut ist. Das Metabolom setzt sich aus Metaboliten zusammen, Metaboliten wiederum besitzen als Stoffwechselzwischenprodukte und/oder ‐endprodukte die Eigenschaft, im gesamten Körper vorzukommen. Um sie zu erfassen, werden sie mittels spezieller Technologien sowohl qualitativ als auch quantitativ gesammelt und ausgewertet. Die gesamte dafür zur Verfügung stehende methodische Palette wird im Rahmen dieser Arbeit vorgestellt.Scientifically observed we reside in the middle of the young OMICS‐sciences and nutritionally observed this circumstance means a great chance to enhance our previous knowledge to probably once optimize nutrition attuned to the individual. This work is concerned with the spectacular area of nutrigenomics which desires to offer a molecular genetic understanding of how common dietary components influence health by changing the expression of structure of an individual´s genetic makeup. As a part of the entire OMICS‐cascade the focus lies on metabolomics as a discipline dedicated to the global study of the whole metabolome. The metabolome again consists of metabolites which are small molecule intermediates or metabolism products with the characteristic potential to optionally appear everywhere within the body. In order to analyze them they get quantitatively but also qualitatively collected and measured by means of a range of techniques. The entire methodological pallet of metabolomic technologies assisting to illuminate nutrigenomic facts will be presented

Magnetoencephalography

This is a practical book on MEG that covers a wide range of topics. The book begins with a series of reviews on the use of MEG for clinical applications, the study of cognitive functions in various diseases, and one chapter focusing specifically on studies of memory with MEG. There are sections with chapters that describe source localization issues, the use of beamformers and dipole source methods, as well as phase-based analyses, and a step-by-step guide to using dipoles for epilepsy spike analyses. The book ends with a section describing new innovations in MEG systems, namely an on-line real-time MEG data acquisition system, novel applications for MEG research, and a proposal for a helium re-circulation system. With such breadth of topics, there will be a chapter that is of interest to every MEG researcher or clinician

Photoassociative Spectroscopy of Ultracold Argon and Krypton Confined in a Magneto Optical Trap

Creating ultracold molecules has attracted considerable interest in the last decade. Once created, such molecules can be used for precision spectroscopy or to study chemical reactions at ultracold tem peratures. Several techniques have been developed to produce ultracold molecules; the most common is photoassociation where two ultracold atoms collide in the presence of light that induces a free-bound transition to an excited molecular state. Photoassociation can also be used to perform spectroscopy in order to map out the ro-vibrational levels of a molecular state. In this dissertaiotn, we report on our Photoasociative Spectroscopy (PAS) studies conducted separately in argon and krypton. For each species, we have studied transitions near two different atomic limits ns[3/2]2 —\u3e np[5/2]2 and ns[3/2]2 —» np[5/2]3where n = 4 for argon and n = 5 for krypton. The former atomic transition is called the “quench transition” since it forms a strong coupled channel to the ground state. As a result for this strong coupling the original atomic sample is degraded and quenched. The latter transition is the one used to cool and confine the atoms and is known as the “trapping transition.” Spectroscopy near the trapping transition in argon was studied previously in our group [1] and specific features were observed in the spectrum. At the time, the features were not definitively identified, but more than one explanation was suggested for further testing. One possible explanation was that these features were a result of resonances happening at “doubly-excited” molecular levels. The population of such states could take place as a result of absorbing two photons of the same frequency which causes photoassociation. In this dissertation we report on a series of experiments that were performed to study and conclusively identify the origin of those features. These experiments led to the conclusion that the features in the spectra were an artifact of otherwise undetectable frequency sidebands on our semiconductor diode laser. Once identified as such, a new laser was constructed to repeat the spectroscopy measurements in argon and take new measurements in krypton that would be free from laser artifacts. In those spectra, no specific vibrational features were observed and resolved in either species. Results were consistent with published results obtained by other groups using other noble gases. Finally, we report on our attempts to perform PAS on a quench transition in order to confirm results obtained for krypton by another group [2]. We were not able to observe any photoassociation signal for both argon and krypton on this transition. We were able to observe similar effects to those reported in Ref. [2] but we attribute these to artifacts from an acousto-optic modulator and not as arising from molecular structure

Microwave-shielded ultracold polar molecules

Since the realization of Bose--Einstein condensates and degenerate Fermi gases, ultracold atoms with tunable interactions have become an essential platform for studying quantum many-body phenomena. Notable examples include the realization of BCS--BEC crossover and the simulation of the Bose/Fermi Hubbard model. Ultracold polar molecules could enrich the quantum gas toolbox with their long-range dipole-dipole interaction, which offers not only new opportunities in many-body physics, such as realizing the topological superfluid and the extended Hubbard model, but also applications in quantum chemistry, quantum computation, and precision measurements. However, the large number of internal degrees of freedom of molecules present a significant challenge in both cooling them to quantum degeneracy and controlling their interactions. Unlike atomic gases, a dense molecular sample suffers from fast collisional losses, preventing the implementation of evaporative cooling and the observation of scattering resonances. In this thesis, we describe how we solved the long-standing issue of collisional losses by microwave shielding, created a degenerate Fermi gas of NaK molecules, and discovered a new type of scattering resonances via which we created the first ultracold tetratomic molecules in the 100-nK regime. By synchronizing the rotation of polar molecules with a circularly polarized microwave electric field, we equip the molecular sample with a highly tunable intermolecular potential. This not only stabilizes the gas against inelastic collisions but also enables field-linked scattering resonances for precise control over scattering lengths. At long range, the molecules interact via their induced rotating dipole moments. As they approach each other, their orientations realign to produce a repulsive force, thereby mitigating inelastic collisions at close distances. With an elastic-to-inelastic collision ratio of 500, we have achieved evaporative cooling of the molecular gas down to 21 nK and 0.36 times the Fermi temperature, setting a new record for the coldest polar molecular gas to date. Thanks to the collisional stability of microwave-shielded molecules, we can directly load them into predominantly a single layer of a magic 3D optical lattice, achieving a peak filling fraction of 24%. These ultracold molecules, owing to their long lifetimes in their ground state and their long-range dipolar coupling, provide a unique platform to study quantum magnetism. With the achieved high filling fraction, we are prepared to study non-equilibrium spin dynamics such as rotational synchronization and spin squeezing. We demonstrated that the interaction between microwave-shielded polar molecules is highly tunable via the microwave power, detuning, and polarization. When the interaction potential is deep enough to host field-linked bound states at the collisional threshold, a shape resonance is induced, allowing us to tune the scattering rate by three orders of magnitude. The field-linked resonances enables controls over the scattering length in a similar fashion as Feshbach resonance for ultracold atoms, promising the realization of strongly correlated phases, such as dipolar $p$-wave superfluid. It also paves the way to investigate the interplay between short-range and long-range interactions in novel quantum matters, such as exotic supersolid. Moreover, through a field-linked resonance, we associated for the first time weakly bound tetratomic molecules in the 100-nK regime, with a phase space density of 0.04. The transition from a Fermi gas of diatomic molecules to a Bose gas of tetratomic molecules paves the way for dipolar BCS--BEC crossover. With microwave-shielded polar molecules, we have realized a quantum gas featuring highly tunable long-range interactions. The technique is universal to polar molecules with a sufficiently large dipole moment, and thus offers a general strategy for cooling and manipulating polar molecules, and for associating weakly bound ultracold polyatomic molecules. Utilizing the toolbox developed in ultracold atoms, this platform possesses the potential to unlock an entirely new realm of quantum simulation of many-body physics