The formation of carbonaceous and silicate precursor molecules to astrophysical dust grains is investigated. Using density functional theory (DFT) in combination with global optimization techniques, the ground-state binding energies of dust precursors are determined. These results are employed in atomistic nucleation theory (ANT) to predict the critical size and nucleation...
Gamma ray bursts (GRBs) are short, intense pulses of gamma rays that emit radiation in a narrow beam. Unless the beam is oriented towards the observer, it is often difficult to resolve the bursts against the diffuse gamma ray background (DGRB). The DGRB is a measured source of gamma rays...
The binding energies of n < 100 carbon clusters are calculated using the ab initio density functional theory code
Quantum Espresso. Carbon cluster geometries are determined using several levels of classical techniques and further
refined using density functional theory. The resulting energies are used to compute the work of cluster...
During AY 2009/10 OSU Libraries’ Research and Innovative Services Department (RIS) conducted a pilot project on “environmental scanning.” One of our goals for the year is to develop a process to investigate emerging trends based on a topic and disseminate our findings. Initially we each scanned a segment of the...
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American Astrophysical Society’s
Astronomical Journal and the product is named AJ Compilations. The
In this dissertation, I present electronic spectra of a few polycyclic aromatic hydrocarbons (PAHs): tetracene, pentacene, pyrene, benzo[g,h,i]perylene and benzo[a]pyrene using resonantly enhanced multiphoton ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The work of tetracene and pentacene also combine a laser desorption source with a ZEKE spectrometer, demonstrating...
In this dissertation, I describe spectroscopic studies of jet-cooled polycyclic aromatic hydrocarbons (PAH) and one nitrogen substituted PAH (PANH) using pulsed field zero kinetic energy (ZEKE) photoelectron spectroscopy and resonantly enhanced multiphoton ionization (REMPI) spectroscopy. Recently, there has been a demand for far-infrared (FIR) spectral information of astrophysically relevant molecules...
Gravitational waves (GWs) are disturbances in spacetime that can be caused by events such as black hole mergers and supernovae, as well as continuous sources such as binary star systems. GWs offer a new avenue of astrophysical research and can reveal information about the early universe. GW detection can be...
We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[a]pyrene (BaP) via resonantly enhanced multiphoton ionization (REMPI). Our analysis concentrates on the vibrational modes of the first excited state (S₁) and those of the ground cationic state (D₀). Similar to pyrene, another peri-condensed polycyclic aromatic hydrocarbon we have investigated, the...
The discovery of GW170817 provided the first empirical evidence that merging binary neutron star systems are both progenitors of short gamma-ray bursts, as well as the primary sites of the nucleosynthetic rapid-neutron capture process. Initially detected as gravitational wave (GW) and gamma-ray burst (GRB) triggers, GW170817 was well-localized and follow-up...
Short gamma-ray bursts (GRBs) are explosions of cosmic origins believed to be associated with the merger of two compact objects, either two neutron stars or a neutron star and a black hole (BH). The presence of at least one neutron star has long been thought to be an essential element...
From the earliest English colonization to the present day, there
has been interest in astronomy in this country. The purpose of this
thesis is to show how the science of astronomy developed in America
from the earliest observations by educated colonists using imported
instruments and publishing in European journals, to...
Computational simulations of disks are becoming an important tool to predict the the evolution of protostars and disks to better understand the formation of planets. Past research has shown that the evolution of disks and their protostar can be altered through the interaction between gravity and hydrodynamic instabilities. We perform...
Core-collapse supernovae (CCSNe) are considered to be important contributors to the primitive dust enrichment of the interstellar medium in the high-redshift universe. Theoretical models of dust formation in stellar explosions have so far provided controversial results and a generally poor fit to the observations of dust formation in local supernovae....
One of the most important unresolved issues in gamma-ray burst (GRB) physics is the origin of the prompt gamma-ray spectrum. Its general non-thermal character and the softness in the X-ray band remain unexplained. We tackle these issues by performing Monte Carlo simulations of radiation-matter interactions in a scattering dominated photon-lepton...
Studying the evolution of the Milky Way galaxy helps us understand our place in the Universe. Early evolution of the Galaxy can effectively be studied by observing stars with low metallicity values since they are the oldest stars still visible. Due to the formation of the Galaxy, the oldest stars...
We present an analysis of the relationship between spectral lag and luminosity in time-resolved segments of long gamma-ray bursts detected by BATSE, an experiment aboard the Compton Gamma Ray Observatory satellite. For full bursts, there is a well-established correlation between the lag, which is easily computed, and the total burst...
We study the late-time (t > 0.5 days) X-ray afterglows of nearby (z < 0.5) long gamma-ray bursts (GRBs) with Swift and identify a population of explosions with slowly decaying, super-soft (photon index Γx > 3) X-ray
emission that is inconsistent with forward shock synchrotron radiation associated with the afterglow....
Gamma Ray Bursts (GRBs) are the most energetic explosions in the Universe, producing up to $\sim10^{53}$ ergs of energy in the first few seconds of their emission -- the so-called prompt phase that is dominated by high energy X-ray and $\gamma$-ray photons. The very large luminosities released in these events...
Detecting gravitational waves is a topic at the forefront of physics. The first gravitational wave was detected by LIGO in 2015. This wave had a frequency in the 10s of Hz. This project is focused on detecting gravitational waves on the nanohertz spectrum using a pulsar timing array. This array...
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is an international collaboration that seeks to use perturbations in the time of arrivals of pulsar signals to detect gravitational waves in the nanohertz range of frequencies. The 15-year data set will be released as of June 2023. It is a...
E+A galaxies represent an important niche in galaxy evolution as a subset of post-starburst galaxies. Set apart from other post-starburst galaxies by their rapid quenching of star formation, E+As are thought to have started their formation outside a galaxy cluster's center and have fallen inward due to gravity; the star...
The education (particularly graduate education) of Americans
who were active in astronomical research between 1876 and 1941
is assessed for its effectiveness in preparing the astronomers for
careers in research. This period contains three dynamic changes:
the growth of American astronomy in becoming the world's leading
community of astronomers, the...
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2 1 .5 Numbers of Doctorates in Different Astrophysical
Fields
Gamma ray bursts are some of the brightest events in the entire observable universe. Since the late 1960’s, thousands of gamma ray bursts have been observed and they have been researched extensively. However, there are still many mysteries which remain unsolved. One such mystery is whether or not the viewing...
I led a collaborative project involving a search for an evidence of a gravitational wave background (GWB) with all the spatial correlations allowed by general metric theories of gravity using NANOGrav’s 12.5 year data set. The search found no substantial evidence in favor of the existence of such correlations.
The...
Given the recent advancements in the field of pulsar timing pertaining to the detection of a stochastic gravitational wave background (GWB), it is now the perfect time to perform tests of gravity via exploration of the correlation signature between the timing data of pairs of pulsars induced by the polarization...
We analyze merger parameters of binary black hole systems (BBHSs), including orbital separation and time at which gravitational and viscous timescales intersect for all combinations of black holes (BHs) in the range 1-100 solar masses. Our initial examination of BBHS merger parameters using the assumption R=0.5r reveals suspicious trends in...
We report zero kinetic energy (ZEKE) photoelectron spectroscopy via resonantly enhanced multiphoton ionization (REMPI) for benzo[e]pyrene. Extensive vibronic coupling between the first electronically excited state and a nearby state allows b₂ symmetric modes to be observed which would normally be Franck-Condon (FC) disallowed. These vibronic modes are comparable in intensity...
Future satellite missions like NASA’s upcoming Magnetospheric Multiscale (MMS) mission are targeting reconnection diffusion regions at the Earth’s magnetopause. These diffusion regions are small compared to the total surface area of the magnetopause. Furthermore, the location of the diffusion region depends on external parameters such as the current state of...
We construct a Monte Carlo simulation in Python to calculate optical flashes at 5x10¹⁴ Hz peaking at 6x10³¹ erg s⁻¹Hz⁻¹St⁻¹ due to synchrotron radiation from the reverse shock of a gamma-ray burst’s jet. While analytical solutions to this problem exist, they rely on sweeping simplifications of what is necessarily a...
We report vibrational information of both the first electronically excited state and the ground
cationic state of jet-cooled triphenylene via the techniques of resonantly enhanced multiphoton
ionization (REMPI) and zero kinetic energy (ZEKE) photoelectron spectroscopy. The first excited
electronic state S₁ of the neutral molecule is of A₁' symmetry and...
Kelvin-Helmholtz (KH) instability, characterized by the distinctive finite-amplitude billows it generates, is an important mechanism in the development of turbulence in the stratified interior of the ocean. In particular, it is often assumed that the onset of turbulence in internal waves begins in this way. Clear recognition of the importance...
The local and remote sources of variability of the South Atlantic Ocean are investigated using a set of numerical experiments and satellite data. A global, eddy-permitting, numerical simulation is analyzed to investigate the dynamical links between the Antarctic Circumpolar Current (ACC) and the Malvinas Current (MC). The model results indicate...
This thesis conveys the key technical features and scientific applications of a particle-particle ballistic simulation tool (SpaceLab) as well as a high level overview of experiments it was designed for and executed on. SpaceLab simulates spherical particle interactions under any combination of self-gravity, sliding friction, rolling friction, Van-Der-Waals (VDW) cohesion...
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) times periodic signals from pulsars as a method of detecting gravitational waves. NANOGrav detects waves emitted in the nanohertz frequency range, a range lower than those previously explored by other organizations. This allows for the study of rarely observed sources such...
Beginning in the late-nineteenth century, several dialogues emerged concerning life on Mars. Some supported the notion of an inhabited Mars, citing recent observations of the planet, while others, pointing to a lack of concrete evidence, denied the validity of such a bold hypothesis. The dialogues within and between different...
The theory behind magnetohydrodynamics (MHD) is utilized to present a 3-D solution to how the induced magnetic field changes with respect to time. Several MHD-based assump- tions are made to simplify the coupling of Maxwell’s equations with two constitutive laws and Ohm’s law. The velocity field is assumed to be...
In this project we measure the neutron capture cross section of ²⁰⁸Pb. We began by calibrating our silicon detector with ²⁰⁴Tl. Two experiments were then performed, the first in December of 1999 and the second in March of 2000. Both experiments were performed in the nuclear reactor of the Radiation...
High-resolution mass spectrometry was used to measure a range of volatile organic compounds (VOCs) in real time as they were produced by the ubiquitous marine cyanobacterium Synechococcus WH8102 during a 24-hour light/dark cycle. Ethenone, acetaldehyde, ethanol, isoprene, acetic acid, dimethyl sulfide (DMS), acetone, phenol, and several as-yet unidentified compounds were...
Results are provided that highlight the effect of interfacial discontinuities in the
diffusion coefficient on the behavior of certain basic functionals of the diffusion, such
as local times and occupation times, extending previous results in [2, 3] on the behavior
of first passage times. The main goal is to obtain...
We report zero kinetic energy (ZEKE) photoelectron spectroscopy of benzo[h]quinoline (BhQ) via resonantly enhanced multiphoton ionization (REMPI) through the first electronically excited state S₁. From the simulated REMPI spectra with and without Herzberg–Teller coupling, we conclude that vibronic coupling plays a minor but observable role in the electronic excitation to...
Outflowing streams of matter or jets are a common phenomenon in the observeduniverse. The most extreme and powerful jets are relativistic, i.e., they travel at speedscomparable to the of speed light. Gamma Ray-Bursts (GRBs) and Active Galactic Nuclei(AGNs) are two sources of these relativistic jets. In this work I will...
Hypothetical power dissipation by a tidal in‐stream energy conversion device was calculated for Admiralty Inlet, Washington, a highly energetic entrance channel to Puget Sound and currently a candidate for tidal energy development. Power dissipation was calculated for a device of a given capacity as a function of hub height above...