The Physics and Astronomy Department at Pomona has extraordinary access to research equipment and facilities, and we encourage our students to undertake research. Below are recent projects that students completed via Pomona's Summer Undergraduate Research Program.

2019

Modulated Amplitude Reflectance Spectroscopy to Spatially Map Charge Carrier Density and Mobility in Organic Field Effect Transistors

Yannai Kashtan ’20; Advisor: Janice Hudgings​

Semiconducting polymer (SP)-based devices such as solar cells and organic field-effect transistors (OFETs) are potentially cheaper, less toxic, and more versatile than silicon-based devices. However, SPs have comparatively low charge carrier mobilities, limiting device efficiencies. A better understanding of spatial variation in charge carrier concentration and mobility will improve our understanding of SPs and pave the way for developing more efficient SP devices. In this work, we use OFETs as a model system in which to spatially map charge carrier density and mobility using a novel modulated amplitude reflectance spectroscopy (MARS) imaging technique.

We optimized poly(3-hexylthiophene) (P3HT) organic field effect transistor (OFET) synthesis for ambient conditions, a process traditionally performed in a glove box. We extracted charge carrier mobilities from MARS and from transfer curves and found them to be self-consistent and to fall between 5•10-5 and 5•10-4 cm2/(V•s). Using MARS, found a roughly square root dependence of carrier drift velocity on effective lateral field. Since there is a quadratic relationship between drift velocity and lateral field at constant mobility, our finding suggests no mobility dependence on lateral field. We report our ongoing work to extract spatially-resolved mobility from MARS phase images, which would allow for better mobility mapping and for exploration of the independent effects of gate and drain bias on mobility.

Up & Coming Molecules for Parity Studies: BaF, AlCl, & YbOX

Graceson Aufderheide ’20, William Ballard ’20, and Alex Preston ‘21; Advisor: Richard Mawhorter​

Although the Standard Model (SM) has enhanced our understanding of particle physics, it is unable to fully explain observed asymmetries in the universe. To expand the SM, physicists seek to understand parity non-conservation (PNC) in molecules, e.g. through the electric dipole moment of the electron (eEDM). Using Fourier transform microwave (FTMW) spectroscopy, we determine exotic molecule structures for use in PNC studies. Molecules are excited into quantized rotational energy states inside a microwave cavity. The emission spectrum is then captured, allowing one to precisely determine the molecular energy level spacing for a given molecule by least squares fitting of the Hamiltonian function.

YbF was the first molecule to establish an upper limit for the predicted eEDM, and BaF is currently involved in PNC studies. Further progress can be made using linear combinations of the degenerate bending mode of triatomic YbOH or the CW/CCW axial rotation modes of the methyl group in YbOCH3. As with YbOH, BaOH can enable more sensitive PNC tests.

This summer we successfully measured 41 BaF transitions, 23 YbF transitions, and 1 YbOH transition. This completes our FTMW study of YbF and enhances existing microwave studies of both BaF and YbOH with higher precision measurements. We can now complete our analysis of YbF and significantly improve the previous multi-isotope fit of BaF. Detailed FTMW studies will also help untangle the complex optical spectra of polyatomics like YbOH & YbOCH3.

Computational Modeling of Plasmonic Organic Hybrid Waveguides

Marcus Michel ’20; Advisor: David Tanenbaum​

With increasing rates of data consumption, the demand for efficient data communications has become all the more relevant. As fiber-optic cables transport optical signals with low energy losses and high signal quality, the next component of the information pathway that needs to be optimized is the electro-optic modulators--the devices used to convert electrical data to optical signals. These devices need to be scaled down while maintaining their efficiency in order to better meet the increasing needs of data communications. Through the combined use of plasmonics and organic electro-optics, the Robinson Group at the University of Washington have succeeded in fabricating electro-optic modulators on the micron scale, compared to purely photonic modulators that have lengths on the order of tens of millimeters. Over the past summer, I used the Discrete Dipole Approximation, an electrodynamic modeling software, in order to gain a greater understanding of the electric field profiles inside these modulators. These models can potentially be used to see the effect of different surface modifications on the electric field distributions within the waveguide.

Fabrication And Characterization Of Screen-Printed Perovskite Solar Cells

Adam Dvorak ’21; Advisor: David Tanenbaum​

Perovskite solar cells (PSCs) are an alternative to mainstream silicon solar technologies due to cost-efficient materials, competitive power conversion, and ease of fabrication. We fabricate PSCs by screen printing inks of Titania, Zirconia, and Carbon and infiltrating them with a Perovskite precursor, then record IV curves and spatial current maps.

Supported by Pomona College grants from the Hirsch and Sontag families.

Mapping Metals In Protoclusters With LATIS

Sunny Roades ’20; Advisor: Philip Choi​

We study the extent to which galaxies impact their surroundings by mapping the distribution of metals around galaxies in overdense regions of the intergalactic medium (IGM). To search for intergalactic metals, we first make maps of the high redshift (z~2.4) IGM using a dense network of background star forming galaxies to probe foreground structure. We present 3D tomographic reconstructions of the Lyman alpha absorption field over a 2 x 10^6​ ​h^-3 ​cMpc^3​ ​volume, created using spectra of background Lyman-break galaxies and quasars from the Lyman-alpha Tomography IMACS Survey (LATIS). We identify HI overdensities > 2.5σ in reconstructions and select background galaxies that lie behind each overdensity to produce a composite absorption spectrum of the gas within a typical overdensity. We use this composite to trace the average CIV absorption in overdensities, finding significant CIV absorption persists out to ~ 2 physical Mpc with an average equivalent width of 0.15 ±0.04 Angstroms. We compare our detection to other measurements of CIV in the circumgalactic medium of typical galaxies at the same redshift to place these overdensities in context. These results represent the first statistical measurement of the chemical sphere of influence of high redshift overdensities, direct evidence that galaxies impact their large-scale environment.

Improvement of the Photovoltage of Sb2Se3 Photocathodes for Solar Water Splitting

Bry Hong ’20; Advisor: David Tanenbaum​

Solar water splitting is a form of solar power in that it is uses light to split water molecules into its constituents, hydrogen and oxygen, letting the oxygen escape into the atmosphere and capturing the hydrogen as fuel. Photoelectrochemical water splitting is the method of using semiconductor based electrodes that absorb light and drive the water splitting reaction. Sb_2 Se_3 was chosen as the semiconducting material for its high light absorbance and carrier mobility, in addition to its abundance and low cost. My goal was to improve the photovoltage of Sb_2 Se_3 photocathodes to enhance the overall performance. Photovoltage is maximized when electrons and holes separate and move without recombination. The incumbent photocathode of our lab was a layered structure of FTO glass/Sb_2 Se_3/TiO_2/Pt, and I decided to add a layer of SnO_2 to make FTO glass/Sb_2 Se_3/SnO_2/TiO_2/Pt.  The motivation behind this addition was the tendency of SnO_2 to form favorable conditions with Sb_2 Se_3 and TiO_2 to allow selective transport of electrons in the preferred direction. I deposited the SnO_2 layer by a facile spin coating method, and the performance was measured using an in-house three electrode cell using illumination equivalent to the sun’s. Upon measurement, both the photocurrent and photovoltage of the system improved from the reference photocathode, from 16 mAcm^-1 to 22.5 mAcm^-1, and 0.3 Vrhe to 0.37 Vrhe respectively.

Harvesting Energy from Human Motion Using Piezoelectric Materials

Natal Negusu ’22; Advisor: Gordon Stecklein​

Piezoelectric materials generate electricity when subject to mechanical stress or strain due to the creation of a potential difference. In this research project, we investigate the practicality of a wearable energy harvester that would make use of a piezoelectric material. The piezoelectric material used for the research was a PZT (lead zirconate titonate) bender. Our objective was to establish the parameters of the intrinsic material and use this information to develop a wearable piezoelectric generator. The wearable device would include an SD card data logger to provide feedback and record the electricity produced. Through various lab and field tests used to quantify the efficiency of the device, we were able to determine that the power output is improved by increasing the free end length of the bender. Power output is further maximized by adding proof masses to the end of the bender.  This is due to the resulting decrease in the resonance frequency of the bender. For proof masses beyond 7 grams, we observe a decline in efficiency that we attribute to increased mechanical damping. Our wearable generator produces up to 2.5 mW of power with a capacity factor of 14%.

Thin Film Measurement and Deposition

Haidee Clauer ’22; Advisor: Gordon Stecklein​

Applications of alumina thin films range from transistor encapsulation and biochemical research to coatings that improve the shelf-life of commercial goods. While alumina can be grown through several techniques, atomic layer deposition allows for precise control of atom-level thickness. In this project we designed a simplified system for carrying out this growth technique at a tenth of the cost of a commercial version. To measure the thickness of oxide films similar to those grown by our proposed deposition system, we employed two optical techniques, reflectance and ellipsometry. We built optical models to calculate the thickness based on our measurements, ultimately verifying the consistency of reflectance and ellipsometry for films up to 3000 Angstroms thick. Through ellipsometry, we measured films as thin as 17 Angstroms with uncertainties as low as 3 Angstroms.

Sphagnum Moss Spore Dispersal Mechanism

Guido Dominguez ’22; Advisor: Dwight Whitaker

Sphagnum moss disperses its spores using a vortex ring generated by a pressurized capsule that ruptures on a warm sunny day. This mechanism of spore dispersal enables Sphagnum to carry its spores beyond the turbulent boundary layer where it grows so that they can be carried indefinitely by wind currents, which would not be possible if the tiny spores were launched ballistically.  Here we present a finite element analysis of the explosive spore discharge from Sphagnum capsules using ANSYS Fluent.  By matching the trajectories of vortex rings in our models to high speed videos of capsule explosions we can determine the initial pressure of the capsule.  Moreover by analyzing the flow of vorticity out of the capsule we can determine if the vortex rings produced by Sphagnum are optimal as is seen for the vortex rings produced by animals.

Fabrication and Characterization of Screen-printed Perovskite Solar Cells

Phuong Nguyen 22; Advisor: David Tanenbaum​

Perovskite solar cells (PSCs) are an alternative to mainstream silicon solar technologies due to cost-efficient materials, competitive power conversion, and ease of fabrication. We fabricate PSCs by screen printing inks of Titania, Zirconia, and Carbon and infiltrating them with a Perovskite precursor, then record IV curves and spatial current maps.

Supported by Pomona College grants from the Hirsch and Sontag families.

A Tale of Two Seeds: Analyzing Seed Dispersal Techniques in Euphobia dendroides and Ceiba speciose

Isaac Cui ’20; Advisor: Dwight Whitaker

Evolutionary and ecological pressures force plants to devise clever mechanisms for dispersing their seeds. For example, the common dandelion (Taraxacum officinale) disperses its seeds by wind, which means it needs a structure that can induce drag (to fly in the wind), but it also seeks to minimize the material necessary to create that structure. The dandelion’s solution is to create a porous, disk-like structure, whose porosity is finely-tuned to maximize drag and create stability in the dandelion seed’s flight. The novelty of that solution is suggestive of the value of studying biological structures to find unique fluid dynamic behaviors. We studied two plants primarily: the tree spurge (Euphorbia dendroides) and the silk floss tree (Ceiba speciosa). High speed camera analyses of the tree spurge suggest that its dispersal technique, where it launches its round seeds at a relatively low angle with backspin, may be attempting to maximize lift. Video analysis of the silk floss tree’s dispersal mechanism, where it drops its seeds in a cotton ball-like capsule, suggests the tree attempts to maximize the capsule’s drag in order to fly farther. Our preliminary results suggest that the cotton ball structure, though porous, in fact induces greater drag than a solid sphere, while also having other evolutionary benefits (i.e., less weight and energy expended in developing the capsule).

Defect Characterization In Organic Solar Cells

Alfred Molina ’21 and Valerie Wang ‘20; Advisor: Janice Judgings​

One of the biggest challenges that burdens society today is how to transition to more sustainably renewable energy. One of the most promising avenues for renewable energy in the future is found in solar energy. Polymer based organic photovoltaic devices (OPVs) are drawing attention because they are a more flexible, tunable material, that has the potential of being a much more cost-effective option when compared to other current photovoltaics. However, one obstacle that holds OPVs back is their inevitable defects that result in loss of efficiency. The foundation of our research uses high spatial resolution thermoreflectance imaging to identify defects via hot spots on the cells that lower their efficiency.  For our work we use a thermal imaging camera to identify specific regions of heating on the device to better guide us to where these defects might be. Then, using a standard light microscope, a CCD camera, and a blue LED for illumination, together interpreted by our thermoreflectance algorithm, we obtain spatially resolved measurements of the change in the relative reflectivity (which is proportional to the change in temperature) of the solar cells as the bias voltage is modulated. We use this data to identify hot spots, or defects, in the operating solar cells and examine how the temperature of the defect’s scales with bias power, which helps us to understand the physical origin of the identified defect allowing us to better interpret the mitigation of these OPVs.

The Physics Education Workspace Prototype

Kenneth Ochieng ’22; Advisor: Thomas Moore

Research on learning trends and styles in physics education is limited by the lack of efficient methods to strategically collect information about how students think when solving problems. The Physics Education Workspace would be a computer application that allows students to work on physics problems, and in the process, collect and provide a transcript of a student’s thinking processes and problem-solving techniques. The transcript generated will provide information valuable to physics instructors, physics education researchers, and physics textbook authors. Specifically, the PEWP seeks to address the shortcomings of the recorded interview technique, which is the most common method that education researchers use to collect data about student thinking. The workspace, unlike the time-intensive analysis of a recorded interview, can provide large volumes of data from many subjects simultaneously and economically.

Our immediate goal for the workspace is to build it up into a usable application that will enable students to solve a very limited set of introductory physics problems (for now) and submit their solutions through the application. The workspace will provide essential drawing tools for students, as well as tools for manipulating equations based on physics principles. In addition, it will also provide links to equations when using unknown quantities and will complete the math involved in solving equations with variables.

Material Properties of Pure Iron Using a Split Hopkinson Bar

Oscar Torres ’20; Advisor: Marc Andre Meyers

Currently, material science literature has discrepancies on the strength of pure iron. A complete set of experiments is needed to understand how iron behaves at a variety of conditions, specifically conditions of ultra-high strain rate and pressure. The Split Hopkinson Pressure bar is an experimental apparatus that can measure strain rates of 10^4 s^-1 plus or minus one order of magnitude. In the experiment described here, the strain, stress, and strain rate of iron were tested using the Hopkinson bar. The data is in the process of being analyzed and will be available soon.

Crafting Cryogenic Solutions for CLASS

Eli Loeb ’20; Advisor: Philip Choi

My work on the Cosmology Large Angular Scale Surveyor (CLASS) project at Johns Hopkins focused on the design, construction, and installation of cryogenic supports for their final telescope, as well as the rehabilitation and operation of a cryogenic test-bed for their 90 GHz detectors.  This SURP entailed hands-on work with cutting-edge systems, as well as invaluable experience with the process of creating complex systems.  The CLASS project aims to unlock the secrets of the early Universe via the mapping of B-mode polarization in the Cosmic Microwave Background (CMB).  This polarization in the CMB can only be caused by gravitational waves originating during inflation, an event postulated (yet hitherto unobserved) by physicists to explain several crucial discontinuities between our theories of the creation and current state of the Universe.

I spent my summer working on various problems, following a general method of research, design, testing, then implementation.  A significant portion of my time was devoted to creating a solution to the current support structures used in the previous 3 CLASS telescopes currently deployed / being deployed in Chile.  Over the course of the summer I learned to design parts in SolidWorks and bring them to fruition with my own hands in the machine shop.  My design greatly reduced the complexity of the current system while lowering the load on the cryogenics significantly.  This system will be implemented in their next telescope.

2017

Fabrication and Characterization of Thin-Film OFET and OLED Devices

Ricardo Espinoza ’19; Advisor: Janice Hudgings

Currently, modern electronics is based on metal-oxide semiconductors, silicon most abundantly; however, organic semiconductors have tremendous benefits in both manufacturing time and costs. In addition, certain electronic devices made from organic semiconductors may be biocompatible, opening new avenues for biological sensor technologies. The shortcoming of these organic semiconductors is that they have yet to achieve the efficiency standards of their inorganic counterparts. In an effort to explore ways to improve devices made from these compounds, tests were conducted on field-effect transistors coated with a poly (3-hexylthiophene) (P3HT) active layer. IV curve measurements were obtained from several devices and charge-carrier mobility was determined. The second set of tests were conducted on LEDs made with one of two semiconducting organic active layers: poly (ethylene fluorene) and a newly synthesized carborane-based compound, poly (bisfluorenyl carborane-co-dihexyl fluorene). IV curves were generated to determine the functionality of the devices. Electrically, most of the devices showed signs of good conductivity. There was much variation in the data and some devices did not perform as expected. The next steps will be to construct devices for MARS imaging, which will allow us to map out the charge carrier distribution on the surface of the device and analyze where the densities of charge-carriers are on the device and how we can facilitate the mobility of charge through it.
Funding Provided By: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund

Demystifying High Temperature Superconductivity: An ARPES Study of Cuprate Hg1201

Ben Gregory ’18; Advisor: Scott Medling

Since their discovery in 1986, high temperature superconductors (HTS) have been an active area of research as their underlying physics cannot be accounted for by our conventional theory of superconductivity. The cuprates comprise one of the major HTS families and have been studied extensively with many experimental techniques. Angle-resolved photoemission spectroscopy (ARPES) is an ideal tool for probing the electronic band structure of advanced materials since it can simultaneously measure the energy and momentum of photoemitted electrons. With the highest Tc in the cuprate family, HgBa2CuO4 (Hg1201) has been the subject of much research, yet it remains understudied with ARPES for lack of a charge-neutral cleavage plane. Here we have studied underdoped Hg1201 with ARPES to first and foremost place its properties in the greater context of the cuprate family and to ultimately elucidate the origin of its record Tc. We have accessed the antinodal region of the Fermi surface, allowing us to calculate the Luttinger volume and thus the doping of the material. Additionally, it has been suggested that Hg1201 shows a Fermi liquid-like behavior indicated by a quadratic resistivity. We explored the temperature dependence of the quasiparticle scattering rate and obtained early results that are consistent with this Fermi liquid hypothesis. Upcoming experiments will seek to characterize spectral broadening as well as probe the mysterious pseudogap.
Funding Provided By: The Elgin Fund for Summer Student Research

Characterizing the 300km/s Stream Near Segue-1 Using Survey Data

Wanying Fu ’19; Advisor: Philip Choi

The characterization of stellar streams in the Milky Way halo provides important observational constraints on the LCDM cosmological model, which posits that galaxies form via the accretion of smaller satellites. One such stream, the 300 km/s stellar stream near the dwarf galaxy Segue 1 (300S), was detected in narrow-field spectroscopic surveys, but has not been traced over a wider portion of the sky. In this study, we search for members of 300S in survey data to map out the stream's extent and further characterize its progenitor. We add to the existing catalog of 300S stars by finding new members of 300S in SEGUE-1, SEGUE-2, and APOGEE-2 survey data, and confirm the kinematic association of 300S with an elongated substructure found in both SDSS and PanSTARRS photometric data. From chemical abundance data and a measured stream velocity dispersion of 5.4 km/s, we infer that the progenitor of 300S is a dwarf galaxy. We analyze the chemical abundance data of 300S stars to characterize the stream progenitor’s star formation history, and compare 300S chemical abundances with that of other Milky Way components to infer satellite accretion scenarios.
Funding Provided By: Craddock-McVicar Summer Undergraduate Research Fund

Exploring Acoustic Metamaterials

Alexander Nguyen ’18; Advisor: Alma Zook; Collaborator: William Lamb ’18

This summer, we decided to investigate acoustic metamaterials, specially crafted materials with properties derived more from their engineered structure than from any unusual characteristics of their constituent materials. These materials are capable of exhibiting curious properties in specific frequency ranges, e.g. negative effective density or bulk modulus, and have led to progress in exciting applications like subwavelength imaging and cloaking. Beginning with a one-dimensional analogue, we successfully demonstrated negative effective mass using a system of masses and springs. Then, proceeding along a rather different tangent, we explored the process of designing a specific metamaterial, starting with an arbitrary coordinate transformation and turning it into a set of material parameters. Finite element analysis simulations were performed in an attempt to probe the necessary geometries for creating materials with said parameters. Finally, using additive manufacturing, we attempted to create a ground cloak. The creation and cleaning processes led to substantial flaws in the cloak’s geometry, but subsequent testing yielded results that appear to be mostly consistent with our predictions, with significant signal attenuation around 3000 Hz. However, more work needs to be done to resolve unexpected amplification effects at lower frequencies, and to refine our experimental setup and remove extraneous variables.
Funding Provided By: Sontag Endowment for Physics Fund

Construction and Implementation of a Combined MASS-DIMM System on Table Mountain Observatory

Gabrielle Mehta ’18; Advisor: Philip Choi

Over the past year, the Pomona College 1-meter telescope at Table Mountain Observatory has undergone significant system upgrades. Under the guidance of Professor Philip Choi, Kutay Nazli (PO ’19), Isaac Cui (PO ’20), and Rachel Mochama (SC ’19), along with a team at the Jet Propulsion Laboratory (JPL), including Adam Mitchell (PO ’18), have spent the summer characterizing and optimizing system performance. Specifically, as part of a Pomona College collaboration with JPL, the team focused on improving the telescope’s astrometric capabilities to meet JPL’s ultra-high precision requirements for tracking fast-moving satellites. To achieve this, the team devised and executed tests to characterize the proficiency of the system in terms of its pointing accuracy and tracking stability. Currently, the system has improved sufficiently to be able to track 18th magnitude high-speed near-earth objects reliably on time-scales of hours, however there is more mechanical work that is necessary to achieve even greater precision. Once the system is optimized, the telescope will have useful national security and environmental applications in monitoring space debris, searching for satellites, and discovering near-earth objects with the potential of colliding with the Earth.

This experiment describes the design and production of a combined multi-aperture scintillation sensor (MASS) and differential image motion monitor (DIMM) instrument on Table Mountain Observatory. The purpose of the MASS-DIMM is to provide a complete atmospheric turbulence profile, which allows observers to directly measure overhead seeing conditions. The term seeing describes the degree of optical turbulence within the atmosphere, and is one of the most important criteria for performing ground-based observations. While it is possible to obtain a seeing estimation using a DIMM alone, the MASS-DIMM is able to reconstruct a full atmospheric turbulence profile. A DIMM measures image fluctuations between two images of the same object usually created from two apertures cut into a mask covering the primary mirror. From these fluctuations, the Fried parameter can then be estimated which can then give way to a seeing estimate. However, this estimate does not tell where the distortion occurred, only how big the distortion is. The MASS is able to work simultaneously with the DIMM to restore the vertical turbulence profile. By opening a third aperture in the mask, this third path is then sectioned off into four beams behind the secondary by a series of four tilted annular mirrors whose radii are on the order of the Fresnel radius. From these apertures, four scintillation indices and six differential scintillation indices are used to then reconstruct a vertical turbulence profile.
Funding Provided By: Sontag Endowment for Physics Fund

An attempt to incorporate spin into a gravitational wave simulation program for LISA

Yijun Wang ’19; Advisor: Thomas Moore

The Laser Interferometer Space Antenna (LISA) is a gravitational wave detector consisting of three Sun-orbiting satellites. Similar to its ground-based counterpart, the Laser Interferometer Gravitational wave Observatory, LIGO, LISA is to detect space-time deformations from gravitational waves, but its space-based nature and orbit design improve how precisely we can know about the wave source and allow for detection on a different range of wave sources from LIGO. Ultimately, we extract information on properties of the wave source from the waveform and the phase of the signal. However, instrument noise introduces overall uncertainties, and our grand project objective is to calculate the associated uncertainties for each parameter based on how the parameters contribute to the waveform and the phase in theory. This summer, we attempted to expand an existing LISA simulation program by more realistically modeling the wave source, namely by adding spins to the binary star system. A Pomona graduate wrote a spin simulation code, and firstly we translated this code into the coding language of the master program, Xojo. We enhanced the accuracy of this code while retaining a reasonable computation efficiency. We renovated the master program by adding in spin-related terms and importing the spin code module. The program should replicate the results from the previous no-spin program when spin-related parameters are set to zero, but the debugging process is left as future work.
Funding Provided By: Sontag Endowment for Physics Fund

Microwave Spectroscopy of Exotic Diatomic Molecules PbF and BaF

Yongrak Kim ’18; Advisor: Richard Mawhorter; Collaborator: Jose Munoz-Lopez ’19

Our group set out to better understand four different diatomic molecules: PbF, BaF, YbF, and TaN. Our main interest is the electron’s electric dipole moment (eEDM). This is a predicted tiny charge asymmetry in the electron; the only problem is that the Standard Model eEDM is far too small to measure. However, newer theories predict it may be up to 1010 times larger and possibly attainable. Our task this summer was to develop a more detailed understanding of these molecules actively in use in this pursuit. In June we traveled to Hannover, Germany to use a Fourier Transform Microwave (FTMW) spectrometer. Its high precision is ideal for detailed analysis of the molecules we are working with. Currently PbF and BaF have highest priority. PbF is interesting because of opposite parity states that appear to converge towards zero at the high vibrational level v = 8. BaF, on the other hand, is a popular diatomic that is currently being evaluated for eEDM measurements by a Dutch team that we met with this summer. Our results this summer yielded higher vibrational data (up to v =7) for PbF. Work with the powder precursor BaF2 showed that it is necessary to use a highly reactive metallic Ba sample instead, requiring further efforts to use safely. However, we did create a model of BaF which encompasses all 59 lines of existing data from three isotopes of Ba and vibrational states v = 0-4. This study will be of use to a number of groups currently building experiments to study BaF.
Funding Provided By: Sontag Endowment for Physics Fund

Binary Star System Simulation

Nikolaos Angelos Papastavrou ’20; Advisor: Thomas Moore

In September of 2015, almost 100 years after Einstein published his general theory of relativity, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected the gravitational waves created by the collision of two black holes. The enormous size of the black holes allowed LIGO to detect the energy transmitted through gravitational radiation and thus confirmed the existence of gravitational waves. Not only does this verify general relativity’s results but also it gives theoretical physicists the ability to test the validity of general relativity in the strong-field limit. Many scientists now develop computational models that simulate the behavior of large bodies that produce such gravitational waves. For our project this summer, we created a simulation that models the spins and the orbital angular momentum of a binary star system and displays in 3D how the spin and orbital angular momentum vectors evolve with time as predicted by general relativity until the system coalesces. The goals were both to test the model and to display the evolution for others. We now have a working simulation. For the sake of getting familiar with 3D graphics, we also developed an educational application that shows the electric field of various charge configurations. We adapted and expanded code written by Kelli Rockwell for her 2017 senior thesis, converting it to Javascript and adding new features and enhancements. This helped prepare the way for writing the binary star model.
Funding Provided By: Sontag Endowment for Physics Fund