Dissertations / Theses on the topic 'Metastable neon'

This thesis presents investigations into the collision dynamics of cold metastable neon atoms in a magneto-optical trap (MOT). At very cold temperatures (approx. 1 mK) the atomic interaction occurs at long range and cannot be treated classically as the interaction between two nuclear point particles. In addition, the collision dynamics can be considerably altered in the presence of an optical eld. In this thesis results are presented for collisions that are altered by the presence of an optical eld and also collisions where the optical eld can be neglected. Controlled optical collisions of cold, metastable Ne atoms are performed by using a control laser tuned close to the (3s)3P2 to (3p)3D3 cooling transition. The control laser modies the rate of ionizing collisions by promoting a pair of colliding atoms onto an excited state potential. In order to induce collisions between pairs of trapped metastables, a control laser is tuned to the red of the transition where we measure a factor of 4 increase in the rate for ionizing collisions. We also investigate the eect of optical shielding by tuning the laser to the blue of the transition and observe a factor of 5 suppression in the ionization rate. However, the measured ionization spectrum does not contain resonances due to the formation of photoassociated molecules as predicted by Doery et al [1]. Instead, we observe a broad unresolvable ionization spectrum that is well described by established theory [2]. Collision cross sections are measured for neon in the (3s)3P2 metastable state with ground state, thermal atoms and molecules. The technique is based on the measurement of the loss rate due to collisions with a background gas. Generally, these type of collisions are considered undesirable, however, it is possible to infer information about the collision cross section if the rate of collisions is accurately known. This novel technique is described and collision cross section measurements are presented for metastable neon in the (3s)3P2 state with He, Ne, Ar, H2, O2, and N2. The average thermal energy of the collision ranges from 11 meV to 27 meV and the measurements have relatively small errors, of the order of 10%.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text

This thesis describes two separate investigations into the ionisation of the 3P2 metastable state of neon (Ne) by strong-eld light pulses. The first is an investigation into the ionisation yield of Ne and the second experiment examines the electron momentum distribution of the ionised electrons. Experimental ionisation results were compared to ionisation models via a scaling fit to ion yield and laser intensity. The best laser intensity fit was provided byTDSE based theory with n = 0:82. The effect of the spin state on ionisation yield was also examined, and it was determined that there is an 15:34:6% difference in ion yield between atoms pumped into the stretched mj = 2 states compared to an atomic ensemble with a more even state population distribution. This was an unexpected result that remains unexplained. Experimental measurements of the transverse electron momentum distribution (TEMD) for Ne that is ionised well in the over-the-barrier regime are compared to the TEMD for Ar, which is ionised well in the tunnelling regime. It was observed that as the polarisation of the ionising light becomes circular, the distribution for Ne remains cusp-like, whereas the distribution for Ar broadens and becomes Gaussian. These results are predicted by a theoretical treatment of the interaction with a TDSE model and quantitatively indicate that the free electron is influenced in a non-negligible way by the ionic core in the over-the-barrier ionisation regime. This has implications for the validity of the strong field approximation in this ionisation regime.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text

This thesis describes the development of a rare gas metastable atomic beam apparatus, and its application to atom lithography. The principal component of the apparatus is the supersonic DC discharge source. The source parameters, such as operating pressure, skimmer distance, discharge current and nozzle shape were optimised to generate a bright beam of excited state metastable neon and argon, with typical flux of 5×10¹? atoms sr?¹ and 3×10¹? atoms sr?¹ respectively. This apparatus was used to investigate the pattern formation of self assembled monolayer (SAM) resists prepared on Au/Si samples exposed to metastable beams of Ar* and Ne*, through microfabricated contact masks. Positive and negative tone patterning was observed, with supporting XPS analysis attributing the negative tone resists to contamination from pump oil vapour. The formation of negative tone contamination resists by the metastable neon beam was applied to the generation of micrometer sized Fe structures using contact masks. A 3-step etch process was developed and refined, resulting in 7.5µm Fe microdot structures on a Si substrate. A bright transverse and longitudinally cooled and collimated metastable neon beam source for atom lithography was developed. The transverse atomic beam collimation stage produced a collimated beam flux of of 1.4×10¹? s?¹, with a divergence of 22.8 mrad. Axial slowing of the atomic beam was demonstrated with the development of a Zeeman slower. Numerical simulations were undertaken to calculate the motion of metastable neon atoms in a one-dimensional standing wave light field mask. The simulations show the dynamics and atom distributions for the focusing regime (low power) and channeling regime (high power). Future refinements of the apparatus should allow the realisation of nanofabricated structures utilising optical masking techniques.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Faculty of Science
Full Text

A metastable neon (Ne) beam generated by a liquid nitrogen cooled, DC discharge source was puried to an atomic beam consisting of a single metastable state. The atomic beam was cooled in the transverse direction by a two dimensional optical collimator, slowed in the longitudinal direction by a novel dual beam Zeeman slower, and then guided through a 30 arc by a hexapole magnetic guide. This resulted in a pure, UV free metastable atomic beam with a ux of (4.41.1)109 atoms s1. The metastable neon atomic beam was used to investigate the patterns formed in resist based atom lithography experiments utilising alkanethiol self-assembled monolayer resists. It was observed that very short chain alkanethiols, such as ethanethiol, do not form viable resist layers. They are likely desorbed from the surface during exposure to the metastable beam and replaced by background mechanical pump oil molecules. Above the critical dosage (71014 atoms cm2) these samples react in a manner similar to bare gold samples and form a carbonaceous resist layer. This dosage was found to be signifcantly aected by the vacuum infrastructure, highlighting the role contamination plays in the formation of negative contrast patterns in resist based atom lithography. Using ellipsometry the growth of a carbonaceous lm during exposure to a metastable atomic beam was characterised. The desorption cross-section of carbonaceous material from a silicon surface via Ne impact was determined to be many times larger than the polymerisation cross-section. The values determined, along with simple estimates for the mean residence time, volume, and cross-section of the contaminants involved provide insight for the application of the theory to other metastable atom experimental apparatus. Direct deposition lithography without laser cooling of the atomic beam was achieved and patterning observed for iron atoms with a local average transverse velocity of up to 4 ms1. A broadening of the experimentally deposited samples, from a full width half maximum of 35 nm predicted by simulations to >80 nm on SiOx substrates, was observed. The broadening is attributed to a substrate dependent diusion mechanism and the scattering and interference of the standing wave light mask near the substrate. An initial characterisation of the magnetic properties of co-deposited iron-nickel (Fe-Ni) structures has been conducted using the longitudinal magneto-optic Kerr eect. Variations in the Fe-Ni concentrations infuence the coercivity of the deposited structures. A reduction in the coercive field in regions with line structures was observed when applying a magnetic field parallel to the co-deposited lines. This has been attributed to the nucleation of magnetic domains in regions were the Fe-Ni alloy possesses a lower magnetic moment per atom. A magnetic anisotropy induced by the incident angle of the Ni atomic beam was also observed in regions without nanostructuring.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text

This thesis presents an in-depth study into the characterization and enhancement of a metastable neon laser cooled and trapped atomic beam. The apparatus consists of a standard Zeeman slowed atomic beam loaded into a magneto-optical trap and was designed for applications to electron scattering experiments and photoionization. The efficiency of the metastable neon atomic source was investigated to determine the ideal cathode type for maximum metastable production and optimal atomic beam velocity haracteristics. A series of characterization measurements were performed on the MOT, and the trap volume and population were investigated for a range of trapping and slowing laser intensities and detunings, together with the MOT and Zeeman slower magnetic fields. The volume measurements were compared to standard Doppler theory and it was found that the Doppler model inadequately explained the trap behaviour. It was found that the MOT population characteristics were governed by two processes: two-body losses that limit the trap population at high densities, and the efficiency of the atom capture process which limits the operational range of the MOT over the various parameters. The trap temperature was determined to be 1.3mK via a time-of-flight technique. This was nearly twice that predicted by Doppler theory and the lack of agreement once again suggests the inadequacies in the Doppler theory to correctly model the experiment. The application of the MOT to the photoionization cross-section measurement of the (2p53p)3D3 state of neon was investigated. The MOT decay technique was utilized to measure cross-section values of o351 = 2.9+0.2 -0.3 x 10 -18cm2 and o363 = 3.1 +0.3 -0.4 x 10-18cm2 at the wavelengths of 351nm and 363nm respectively. This is an increase in accuracy of around a factor of five from previous measurements and it was found that the results agreed well with the values predicted by current theories.

This thesis presents an in-depth study into the characterization and enhancement of a metastable neon laser cooled and trapped atomic beam. The apparatus consists of a standard Zeeman slowed atomic beam loaded into a magneto-optical trap and was designed for applications to electron scattering experiments and photoionization. The efficiency of the metastable neon atomic source was investigated to determine the ideal cathode type for maximum metastable production and optimal atomic beam velocity haracteristics. A series of characterization measurements were performed on the MOT, and the trap volume and population were investigated for a range of trapping and slowing laser intensities and detunings, together with the MOT and Zeeman slower magnetic fields. The volume measurements were compared to standard Doppler theory and it was found that the Doppler model inadequately explained the trap behaviour. It was found that the MOT population characteristics were governed by two processes: two-body losses that limit the trap population at high densities, and the efficiency of the atom capture process which limits the operational range of the MOT over the various parameters. The trap temperature was determined to be 1.3mK via a time-of-flight technique. This was nearly twice that predicted by Doppler theory and the lack of agreement once again suggests the inadequacies in the Doppler theory to correctly model the experiment. The application of the MOT to the photoionization cross-section measurement of the (2p53p)3D3 state of neon was investigated. The MOT decay technique was utilized to measure cross-section values of o351 = 2.9+0.2 -0.3 x 10 -18cm2 and o363 = 3.1 +0.3 -0.4 x 10-18cm2 at the wavelengths of 351nm and 363nm respectively. This is an increase in accuracy of around a factor of five from previous measurements and it was found that the results agreed well with the values predicted by current theories.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text

A high flux metastable Neon atomic beam was designed and characterised. Atom optical enhancement of the beam using a two-dimensional optical collimator, novel two beam Zeeman slower and hexapole magnetic guide was performed to produce a UV-free metastable flux of (4.35 × 109 ± 4 × 107) atoms s−1. Investigations of several resists for neutral atom lithography were undertaken. A quantitative investigation of the wetting properties of ethanethiol (ET) and dodecanethiol (DDT) self-assembled monolayers (SAM’s) exposed to various metastable dosages was carried out. A mechanism for the poor lithographic patterning using ET was proposed and the negative contrast patterning observed for this SAM was similar to those observed for bare gold substrates and were attributed to mechanical pump oil (MPO) contamination resists. Negative patterned resists were used to produce 7.5 μm iron dots on a silicon substrate via neutral atom lithography. This scheme was found to be very robust and free from the laser cooling issues of alternative direct depositional schemes. Numerical simulations have shown that two dimensional arrays of magnetic nanodots may be produced this way, paving the way for a magnetic storage option with a density of " 0.1 Gbit mm−2.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text

This thesis presents a new technique for measuring total absolute collision cross sections. Using this technique, the total absolute collision cross sections were determined for neon in the (3s)3P2 metastable state with ground state thermal atoms and molecules. A magneto-optical trap (MOT) is used in this technique which infers the cross sections via the measurement of population dynamics within the MOT to determine the collision cross section. This technique is capable of providing benchmark measurements of total absolute collision cross sections. The measurements are unique for the low average collision energy which ranges between 11meV and 27meV for the dierent collision species and relatively low uncertainty of approximately 9.4%. The measurements were for neon in the (3s)3P2 metastable state with He, Ne, Ar, H2, O2, N2 and CO2. The measured cross sections were respectively 160±20Å2, 500±50Å2, 840±80Å2, 230±20Å2, 1000±100Å2, 1300.0±100Å2, 830±80Å2. The measurements made using this technique have small uncertainties, of the order of 10% of the measured cross section. As Ne* does not have the energy to ionize He, the Ne*-He collision was entirely elastic and the validity of this technique was conrmed by comparing the experimental result for this collision with an approximation for the elastic collision cross section based on van der Waals forces. The calculation based on this approximation yielded an elastic cross-section of 168.88Å2 for the Ne*-He system. This theoretical value compared favourably and within the uncertainties of the experimental measurement for the Ne*-He collision of 160±20Å2. To be able to perform these investigations a rebuild and partial redesign of the Griffith University metastable neon trapping apparatus was necessary and was included in this work.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
Full Text

Etude experimentale de ce pompage optique sur les isotopes **(21)ne, **(83)kr, **(129)xe et **(131)xe afin de mesurer le facteur de lande g(**(3)po) par des experiences de resonance magnetique en phase vapeur (**(21)ne) ou son faisceau atomique, les atomes etant portes dans l'etat metastable a l'aide d'une decharge haute frequence et pompes optiquement par un laser a colorant continu accordable, avec une precision superieure a celle des calculs a partir de la structure hyperfine

Un faisceau d'atomes metastables de neon, dans un etat interne defini (projection plus deux ou moins deux du spin) est prepare par excitation optique laser, en polarisation circulaire. On mesure la difference des deux sections efficaces differentielles obtenues dans les deux cas de polarisation. Pour le systeme symetrique (neon metastable-neon au fondamental), on obtient un comportement oscillatoire a petit angle et a grand angle. Du point de vue theorique, on etablit les proprietes generales de symetrie de la difference, ainsi que son annulation a angle nul et a cent quatre vingts degres. Le calcul de la difference est base sur la determination des amplitudes de diffusion elastiques et inelastiques, avec, pour axe de quantification, l'axe du faisceau incident. La methode jwkb a ete etendue a ce probleme a plusieurs voies couplees. Le calcul demontre la sensibilite aux couplages et donc a l'anisotropie de l'interaction

Ce travail porte sur l’étude et la réalisation d’une nouvelle technique de décélération d’un jet supersonique de particules paramagnétiques en utilisant une onde de champ magnétique progressive co-mobile. Cette technique repose sur une méthode de ralentissement basée sur les forces de type Stern Gerlach agissant sur un système paramagnétique en mouvement en présence d’un champ magnétique co-propageant. Cette méthode très innovatrice a l’avantage de pouvoir s’appliquer à une grande palette d’espèces ouvrant ainsi de nouvelles possibilités d’applications. On décrit une approche théorique adaptée qui permet de faire un lien direct entre la théorie, la programmation des paramètres expérimentaux, les résultats obtenus et ce d’une manière systématique, rationnelle et prédictive.Ce mémoire est composé de trois parties. La première porte sur les forces décélératrices et le calcul des différentes forces, de type Stern Gerlach, utilisées dans nos expériences. Les formules établies dans cette partie sont essentielles pour l’interprétation des résultats expérimentaux. La deuxième partie porte sur le dispositif expérimental : le jet supersonique pré-refroidi, la zone d’interaction et la détection. On donne le détail de la réalisation des circuits créant les champs magnétiques nécessaires au guidage et à la décélération du jet. La troisième partie porte sur les résultats des expériences réalisées et leur interprétation directement à partir des équations du mouvement de l’effet Stern Gerlach. Des simulations sont présentées pour étayer les interprétations. On présente les résultats de décélération obtenus récemment sur l’argon et le néon métastables. Ces résultats valident clairement l’importance de l’ajout d’un champ magnétique uniforme qui définit un axe de quantification adiabatique global pour toutes les particules du jet et permet le découplage entre la précession des moments magnétiques et l’action des forces de gradient. Ces résultats mettent en évidence, aussi, l’effet de polarisation du jet qui dépend du sens relatif du champ magnétique uniforme ajouté par rapport à l’onde de champ magnétique progressive.Enfin, la compréhension et le contrôle de la dynamique du piégeage à une vitesse donnée, de l’accélération et de la décélération nécessitent le découplage entre les effets transverses et les effets longitudinaux de l’onde. Ces derniers sont clairement visibles quand le champ magnétique uniforme ajouté vient limiter les effets transverses de l’onde de champ magnétiques progressive. Les perspectives pour ce nouveau décélérateur Zeeman Stern Gerlach sont grandes. Un premier résultat de piégeage du di-azote métastable à 560m/s est présenté et ceci ouvre la voie pour décélérer les molécules paramagnétiques en jet supersonique pulsé. La décélération des radicaux libres et des neutrons est aussi envisageable
This work focuses on the study and implementation of a new technique of deceleration of a supersonic beam of paramagnetic particles using a co-moving progressive wave of magnetic field. This technique relies on a method of slowing based on Stern-Gerlach forces acting on a paramagnetic system in motion in the presence of a co-propagating magnetic field. This highly innovative approach has the advantage of being applicable to a wide range of species and opens up new opportunities. A suitable theoretical approach is followed, that allows for a direct link between theory, programming of experimental parameters, and experimental results in a systematic, rational and predictive manner.This thesis is composed of three parts. The first concerns the calculation of the various Stern Gerlach forces used in our experiments to decelerate the paramagnetic particles. Formulas established in this section are essential for the interpretation of experimental results. The second part is devoted to the experimental device: the creation of the cooled supersonic beam, interaction zone and detection. A separate chapter is devoted to the detailed description of the different setups of coils used to create the magnetic fields necessary to guide and to decelerate the particles of the beam.The third part is devoted to the experimental results and their direct interpretation using the equations of motion in Stern Gerlach forces. Simulations are presented to embody the interpretations. We present results about the deceleration of metastable argon and neon atoms. These results validate the significance of the addition of a uniform magnetic field defining a global adiabatic quantization axis for all the particles in the beam. This realizes the decoupling between the precession of the magnetic moments and Stern Gerlach forces. The results demonstrate the polarization effect of the beam that depends on the direction of the added uniform magnetic field relative to the progressive wave of the magnetic field.Finally, the understanding and control of the dynamics of trapping at a given speed, acceleration and deceleration require decoupling between the transverse and longitudinal effects of the wave. These effects are clearly visible when the added uniform magnetic field limits the transverse effects of the progressive wave of magnetic field. The outlooks for the new Zeeman Stern Gerlach decelerator are numerous. A first result of trapping di-nitrogen metastable at 560m/s is presented and the road is open to decelerate paramagnetic molecules in pulsed supersonic jet. Deceleration free radicals and neutrons are also possible

In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2]2 and the 3s'[1/2]0 metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. Based on previous measurements we have selected 22Ne for evaporative cooling. Although, we can experimentally achieve an increase in phase-space density with evaporative cooling, the relatively high inelastic collision parameters prevent the realization of a Bose-Einstein condensate in neon. For the measurements described here, neon atoms have been confined in a magneto-optical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m=+2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 1e11 cm^-3, and a central phase-space density of up to 2.2e-7. After loading the optical dipole trap from the magnetic trap, 2.5e6 atoms with typical temperatures of 0.1 mK, and central densities up to 5e10 cm^-3 were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5e-5. Also simulations of optimized evaporation for our experimental parameters show clearly that we are limited to a phase-space density on the order of 1e-5. From these simulations it became clear that a 5-fold increase in the "good-to-bad" ratio for evaporative cooling suffices to reach the quantum degenerate regime. Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the 3D3 line a frequency dependence of laser enhanced Penning ionization was observed, which is interesting in itself. The absence of the collisional enhancement effect by laser light for the transition to the 3D2 line is intriguing and for an explanation calculations are required. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. In the magnetic trap, we are limited to offset fields < 50 G. In this range of fields, the two-body losses are too large to achieve a Bose-Einstein condensate of magnetically trapped metastable neon. The implementation of an optical dipole trap allowed us to trap the 3P0 metastable state. From the trap loss measurements we determined the two-body loss coefficient of the 3P0 metastable state for both bosonic isotopes 20Ne and 22Ne. For 20Ne we obtained ß=6(+5,-4)e-10 cm^3/s and for 22Ne ß=11(+7,-6)e-10 cm^3/s. These large two-body losses make it extremely unlikely to reach degeneracy with this metastable state. Nevertheless it is important that the 3P0 metastable state can be trapped to investigate other interesting physical effects. For example, it is essential to apply the STIRAP technique for trapped atoms and to realize the proposed coherent control of collisions. There is also a large interest in a precise determination of the lifetime of this metastable state, which is of importance for the verification of QED. We can also trap neon atoms in their energetically lowest magnetic substate 3P2(m=-2) with the perspective of reducing inelastic collisions in the energetically lowest state.

In this thesis we investigate theoretically the cold collision properties of metastable neon (Ne*). The collisions of metastable rare gases (Rg*) exhibit a plethora of interesting phenomena: Due to the high internal excitation energies of the metastable atoms ionization processes are very likely. The produced ions can be detected with single-ion efficiency in the experiment. In experiments with atomic Rg* gases at cold temperatures T~1 mK, this allows for in-situ monitoring of the real-time dynamics of the atomic gas and for example for the study of two-particle correlations. Furthermore, in cold Rg* gases one can examine the prospects of creating a Bose-Einstein condensate or a degenerate Fermi gas of Rg*. Ne* is a promising candidate for Bose-Einstein condensation and in the group of G. Birkl the properties of cold gases of Ne* are investigated experimentally. Two-body loss rate coefficients due to the ionization processes and elastic cross sections have been measured. It is useful to complement the experimental measurements with a theoretical study in order to obtain a better understanding of the cold Ne* gases and the collision physics of Ne*. At the low temperatures of the atomic gases, these gases are dilute with particle number densities of n~10^9 cm^{-3}. For these low densities, the behavior of the gas is determined mainly by two-body collision physics which is solved by quantum scattering theory in terms of the S matrix. The collision physics is given by short-range interactions and long-range interactions of the atoms. The short-range and long-range interaction potentials of Ne* have been calculated in the molecular basis of Ne2. In this thesis we first calculate short-range and long-range interactions of atoms and molecular basis states of diatomic molecules with a simpler electronic structure than Ne* and Ne2 in order to introduce the notation and to discuss the characteristics of the calculated molecular interaction potentials and in order to employ them in the scattering calculations for Ne*. Instead of solving the full scattering equations by taking into account all the molecular interaction potentials, we demonstrate that the collision physics of Ne* can be described in terms of a coupled two-channel model with a single interaction potential only which describes the elastic scattering of Ne*. In this model, ionization in Ne* collisions is described by the transition of the upper elastic interaction channel to the lower channel, representing the loss or ionization channel. We introduce two versions of the two-channel model in this work. In the first version, the two channels are given by square-well potentials. We can solve the scattering equations analytically and for complex wave numbers k and study the solutions in the complex k plane. With an expansion of the S matrix in terms of its poles in the complex k plane we find a parametrization of the two-body loss rate coefficients. We show that these coefficients describe ionizing collisions of Ne* by comparing them to the experimental measurements and to the numerical results obtained by the two-channel model in the second version. In this second version of the two-channel model, the elastic scattering channel is given by a realistic interaction potential of Ne*, consisting of a calculated short-range and long-range molecular potential, and the loss channel by a model ionization potential. For this model we calculate the two-body loss rate coefficients and the elastic cross sections for the isotope mixtures of Ne* which have been measured experimentally and demonstrate that the free potential parameters can be optimized to the experimental data to achieve very good agreement of the numerical results with the experimental measurements. We discuss the validity of the two-channel model by comparing the results to existing models for cold Rg* collisions and find that the two-channel model of this work is a useful extension to these models.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1988.
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