▼ The thesis documents the work done over the year to initiate an undergraduate Advanced Laboratory experiment which tests Bell’s inequality. It provides reference theory for the experiment, including explanations of Bell inequalities, basics of nonlinear optics, type-I downconversion and entanglement, and polarization states of the entangled photons. A main result is the equipment and design proposal for the experiment, which will cost a total $19600, led in price by the $9000 of a four photodetector array and followed by the $5000 of a 405nm pump laser. Entangled photons are produced by pumping BBO in a two-crystal geometry. Although most of the light is transmitted, some undergoes type-I parametric downconversion. Degenerate pairs are in a tunable entangled state and can be used to show non-classical behavior. Specifically, a violation of the CHSH Bell inequality can be observed. Usable coincidence rates of several thousand per second are expected. Experimental and data analysis methods are described as the basis of future laboratory documentation. Explanations of equipment alignment and adjustment and data collection are included, as well as derivations of relevant analyses of the experimental data. Lastly the coincidence circuit built for the experiment is reviewed. The circuit costs less than $40 to construct and demonstrates a coincidence window of between 18ns and 36ns. Advisors/Committee Members: Fitgerald, Stephen.

▼ An optically thin layer of carbon monoxide in the Earth's mesosphere results in strong, sharp emission peaks at CO's rotational transition frequencies. The J = 2 → 1 and J = 4 → 3 transitions were observed by the Antarctic Sub-millimeter Telescope / Remote Observatory (AST/RO), located at the Amundsen-Scott South Pole station. Mesospheric wind speeds were calculated from the Doppler shifts in emission spectra, as determined by least-squares fitting Advisors/Committee Members: Martin, Christopher.

▼ Precision spectroscopy measurements have contributed significantly to our understanding of the fundamental structure of atoms. Here we present an experiment involving a new precision spectroscopic technique using a femtosecond optical frequency comb to excite two-photon transitions in rubidium. A femtosecond optical frequency comb is an ultrashort, pulsed laser with tens of thousands of frequencies, equally spaced in frequency-space. These frequencies can be used to excite atoms to specific transitions. The frequency comb is a versatile instrument that can avoid many of the experimental uncertainties that are associated with other spectroscopic techniques. The specific technique we use is called velocity selective resonance, and it is used to eliminate Doppler broadening in our spectra. In addition, the setup could be cheaply and easily altered to study different atoms or systems. In this experiment, we study this new precision measurement technique of using an optical frequency comb for spectroscopy. Advisors/Committee Members: Stalnaker, Jason.

▼ Diffuse reflectance infrared spectroscopy is used to measure the quantum dynamics of molecular hydrogentrapped within a C60 lattice at temperatures as low as 10 K. Crystal field effects in conjunction with rotational translational coupling lead to a rich spectrum with multiply split peaks that are more than an order of magnitude sharper than at room temperature. The induced redshifts in the vibrational-rotational mode frequencies are explained using a simple model in which the state dependence of the H2 polarizability leads to changes in the C60-H2 interaction potential. Advisors/Committee Members: FitzGerald, Stephen.

▼ The hydrogen molecule ion is the simplest molecule, consisting of only two protons and an electron. As such, understanding this problem is essential in order to extend quantum mechanical techniques to more complex molecules such as the next simplest hydrogen molecule. The non-ionized hydrogen molecule represents the simplest system with only axial symmetry exhibiting Pauli exclusion principle effects due to the two identical electrons (fermions) in the neutral molecule. Both molecules have been treated in great detail both experimentally and theoretically and the nature of their solutions and energies are well understood. Dimensional scaling of the problem can provide insight into the nature of the exact solutions to a system. For example, the problem may be solvable in certain dimensions other than three due to the simplicity of the problem or some symmetry that is present in other dimensionalities. In the present work, the former results in the hydrogen molecule ion being exactly solvable in closed form in one dimension. Solutions for the energies for a scaling of the hydrogen molecule ion Hamiltonian done by Herschbach et. al. and by Lopez et. al. [M. Lopez-Cabrera, A. L. Tan, and J. C. Loeser, J. Phys. Chem., 1993, 97, 2467-2478. and D. D. Frantz and D. R. Herschbach, J. Chem. Phys., 1990, 92, 6668-6686.] results in the energy for the three-dimensional problem being bounded by the D→1 and D→ ∞ limits, both of which can be solved in closed form. [T. C. Scott, M. Aubert-Frecon, and J. Grotendorst, Chemical Physics, 2006, 324, 323-338.] In the present work, a model of the one-dimensional hydrogen molecule ion is developed in which the charge distributions and electric fields are both mathematically fully described in one dimension. The wavefunctions governing the spacial coordinate for this model were found to be combinations of Airy functions of the first type and the wavefunctions for a free particle (sine and cosine functions) and the energies were found to be similarly governed by the Airy function and trigonometric functions. Various physical interpretations of this model are introduced with example numerical calculations. In one interpretation, the model describes a single electron bound between two plates of positive charge. The results of this problem assume that the plates are fixed in space and have a relatively simple function governing the energies. Another interpretation assumes that the particles in one dimension are uniform in charge and area, making it appropriate for application to the hydrogen molecule and for comparison to the hydrogen atom. Numerical analysis of these results show that the molecule will have lower energy than un-bonded hydrogen atoms, suggesting that this molecule will bond. The scaling of units with the dimensional scaling performed is briefly discussed in the process. There are some difficulties associated with the dimensional scaling of units of charge, energy, and mass in a physically reasonable way that solves the problem. Some elegant mathematical relationships that help provide insight into possible solutions for this problem are presented, but the problem is left unresolved, resulting in a barrier for generalization of the model to dimensionalities greater than three. Suggestions for other potentially illuminating extensions on the work are made. One is some possibilities for extension of the physical interpretation of the problem to the hydrogen molecule based on a change of variables suggested by Goldman [S.P. Goldman, Phys. Rev. A, 1998, 57, R677-R680.]. Others include techniques for three dimensions and beyond for the hydrogen molecule and hydrogen molecule ion respectively. Advisors/Committee Members: Styer, Daniel.

▼ Though pulsar timing has confirmed the existence of gravitational waves, no technique has directly detected them. Jenet et al. state the requirements for the Parkes Pulsar Timing Array (PPTA) to make a significant detection of the stochastic gravitational wave background within five years. By employing the scintillation information in observations for each pulsar at every epoch, I believe interstellar scattering, an underestimated source of timing noise, can be corrected enough for the PPTA to meet these requirements. The improved detection threshold will help answer important questions about black hole mergers, galaxy evolution, and gravitation. Advisors/Committee Members: Stinebring, Daniel.

▼ The purpose of this investigation is to assemble an apparatus capable of testing Bell’s inequality for a local hidden variable. The historical context and theoretical developments that led to this area of inquiry are presented. Expected experimental results stemming from two distinct physical theories are introduced. Procedures are given that outline the assembly of a device capable of testing these theories. Analysis confirming the successful completion of a majority of the steps is presented, and the final necessary steps are detailed. Finally, a laboratory prompt for this experiment’s use in Oberlin College’s advanced laboratory class is given. Advisors/Committee Members: FitzGerald, Stephen.

▼ We have used pulsar scintillation observations to probe the ionized component of the interstellar medium on AU size scales. Previous work had shown that the presence of scintillation arcs in pulsar secondary spectra requires that the scattering along the line of sight to the pulsar is dominated by a thin screen of scattering material. An isotropic image gives rise to a sharply delineated arc, while an anisotropic image with refractive "hot spots" elongated along the pulsar velocity vector gives rise to detailed substructure and arclets in the secondary spectrum. Twenty-five years of archival scintillation data from the Arecibo Observatory show that arclets are present in ~ 25% of low radio frequency observations of PSR B0834+06 and PSR B1133+16 and that the decorrelation time scale of substructure is ~ 6 months. Observations of the pulsar PSR B0834+06 at Arecibo identified four isolated arclets at high delays. These arclets were present throughout a month of observations, and their angular separation from the pulsar changed over the course of the month in a linear fashion. This transverse motion is dominated by the velocity of the pulsar and implies an approximate upper limit to the screen velocity of 7 km s-1. We applied a plasma lens model to these observations assuming that the high delay arclets are caused by refracting plasma lenses in the scattering screen. We place an upper bound of a ~ 0.1 AU on the lens size and estimate an electron density within the lens of ne ~ 200 cm-3. The ionized component of the lens thus has a mass of Ml ~ 10-18 Msun. These parameters are very similar to the predicted parameters for the plasma lenses thought to cause Extreme Scattering Events in quasars. Advisors/Committee Members: Stinebring, Daniel R.

▼ In this thesis we examine the hydrogen storage properties of four different materials. Because of the global climate crisis and the growing realization that petroleum resources are limited, there has been a strong push to find alternative means of energy storage. At the forefront of this push is the hydrogen economy, the idea that hydrogen gas is a bountiful, clean, alternative means of energy storage. One step towards realizing the hydrogen economy is finding a practical means of hydrogen storage. The conventional methods of hydrogen storage are in high-pressure gas cylinders or as a liquid. Both of these methods are impractical for energy storage purposes. The gas cylinders are very massive and so hold little hydrogen for their weight; and hydrogen only liquefies at -251.9° C (-421.4° F), which imposes impractical limitations on its use. The most promising alternative storage option is finding a material that traps a large quantity of hydrogen at room temperature and atmospheric pressure. At the current time, there is no known material that is a practical option for hydrogen storage. In this thesis we use infrared spectroscopy to investigate the behavior of the hydrogen inside the material and the interaction between the trapped hydrogen and the material . By refining our understanding of this interaction, we can predict what might make good storage materials. Currently, theoretical models are unable to predict energies that are correct within 25%. We successfully explain the observed behavior of the trapped hydrogen in the four materials. Our investigation also provides a wealth of data that can be used to calibrate theoretical models. These results will help guide us towards new materials that have greater potential to be viable storage alternatives. Advisors/Committee Members: FitzGerald, Stephen.

▼ This thesis discusses research being done to understand the inner parts of the Milky Way Galaxy. We already know that there are dense star clouds, a supermassive black hole, and a large bar structure, but much of the inner galaxy is shrouded in mystery. Dust absorption, for one thing, prevents us from seeing the galactic center directly with our eyes. To help understand the elusive inner Milky Way, we examine radio telescope data taken in Antarctica by Oberlin College Professor Chris Martin. His gigahertz radio observations were already analyzed to help understand how gas funnels into the Milky Way's supermassive black hole. We study this data further to characterize turbulence and predict how hot or cold the gas is. The analysis of this data will also help prepare for the next thing: Herschel Space Observatory. This European telescope is scheduled to be launched in late April and will begin taking data in the fall of 2009. Chris Martin was granted 125 hours of observation time on the telescope to study the Inner Milky Way. Advisors/Committee Members: Martin, Chris.

▼ There are a range of environmental and industrial applications to capturing carbon dioxide from gas mixtures. Currently, materials being used in these applications bind carbon dioxide too strongly for practical purposes, such that they require large amounts of energy to be regenerated for reuse. Highly porous materials called metal-organic frameworks (MOFs) could serve much more effectively as carbon-capturing materials, as they suck up large amounts of carbon dioxide gas at pressures and temperatures that are nearly ideal for carbon-capture applications. Moreover, they require much less energy than current materials to release the carbon dioxide and be regenerated. Additionally, many different structures can be created fairly easily, so scientists are on the hunt for the ideal carbon-capturing MOF. In this thesis we study Mg-MOF-74, a particularly promising metal-organic framework material for separating carbon dioxide from gas mixtures. We use infrared spectroscopy to probe the interactions between the Mg-MOF-74 host and both carbon dioxide and methane. By shining infrared radiation on Mg-MOF-74 with gases trapped in it and looking at which frequencies of radiation are absorbed by the bound gases, we can learn about the binding nature of the framework. This in turn helps us to better understand the properties are are preferable in metal organic frameworks, and will aid chemists in fabricating new structures that are ideal for carbon-capture and other applications. Advisors/Committee Members: FitzGerald, Stephen.

▼ Since its onset in 1941, matrix isolation has become a popular and common technique for studying species using spectroscopy by isolating them in an inert host solid [1]. Due to the large, spherical shape of the molecules, solid C60 has large interstitial voids making it a good host for matrix isolation. These voids come in two varieties. The larger of the two, the octahedral sites, have an ideal size for studying the dynamics of H2 molecules because the sites are large enough that a hydrogen molecule can be trapped, resulting in quantized translational motion, and can rotate nearly freely within the site. On the other hand, the sites are also small enough that each will contain only one hydrogen molecule thus eliminating H2-H2 interactions. The dynamics of a single hydrogen molecule isolated within the potential well of an octahedral site are very interesting because it represents a real-life example of the famous quantum mechanical situation of a “particle-in-a-box”. While the quantum dynamics of hydrogen within a C60 host lattice is worthy of investigation purely on the basis of the interesting physics involved in the system, there is also a practical importance for gaining a better understanding of the C60-H2, host-guest interaction because of the continuing interest in the possible use of carbon nanostructures as devices for hydrogen storage 3]. Using infrared spectroscopy to study H2 intercalated within a C60 lattice gives insight into the nature of the C60-H2 interaction because H2 is not infrared-active under normal conditions and so the H2 absorption peaks in our spectra are purely due to interaction with the C60 host. Initial results the H2 absorbance spectrum were published in 2002 by Professor Stephen FitzGerald, Scott Forth, and Marie Rinkoski [4]. This paper presents a continuation and a further understanding of using Fourier transform infrared spectroscopy to study the quantum behavior of H2 molecules within the octahedral lattice sites of C60. Advisors/Committee Members: FitzGerald, Stephen.