Master of Science

thesisA multiple-box model was designed to determine how anthropogenic, biological, and meteorological processes combine to produce diel cycles of carbon dioxide (CO2) concentrations within the urban Salt Lake Valley (uSLV). The model was forced by an anthropogenic CO2 emissions inventory, observed winds, sounding-derived mixing depths, and net biological flux estimates based on temperature, solar radiation, day of year, and ecosystem type. The model was validated using hourly CO2 data from a network of sensors around the uSLV for years 2005-2009. The model accounted for 53% of the observations on an hourly basis and accounted for 90-94% of the mean diel cycle of the observations depending on the season. Salt Lake Valley suffers from prolonged temperature inversions during the winter that trap pollutants and gases at the surface. The CO2 network (co2.utah.edu) was compared with the CO2 multiple-box model to determine whether the model could capture the main drivers of CO2 variability during the Persistent Cold Air Pool Study (PCAPS). Time-height analyses were performed to facilitate investigation and explanation of CO2 variability during PCAPS intensive observation periods (IOPs). The analyzed data included atmospheric soundings, CO2 network data, quasivertical CO2 profiles collected ascending by foot or vehicle, and laser-ceiliometer data

Electron–Nuclear Interaction in 13C^{13}C Nanotube Double Quantum Dots

For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variable concentration of $^{13}C$ (nuclear spin $(I=\frac{1}{2})$ among the majority zero-nuclear-spin $^{12}C$ atoms. We observe strong isotope effects in spin-blockaded transport, and from the magnetic field dependence estimate the hyperfine coupling in $^{13}C$ nanotubes to be of the order of $100 \mu eV$, two orders of magnitude larger than anticipated. $^{13}C$-enhanced nanotubes are an interesting system for spin-based quantum information processing and memory: the $^{13}C$ nuclei differ from those in the substrate, are naturally confined to one dimension, lack quadrupolar coupling and have a readily controllable concentration from less than one to $10^5$ per electron.Physic

Relaxation and Dephasing in a Two-Electron 13C^{13}C Nanotube Double Quantum Dot

We use charge sensing of Pauli blockade (including spin and isospin) in a two-electron $^{13}C$ nanotube double quantum dot to measure relaxation and dephasing times. The relaxation time $T_1$ first decreases with a parallel magnetic field and then goes through a minimum in a field of $1.4 T$. We attribute both results to the spin-orbit-modified electronic spectrum of carbon nanotubes, which at high field enhances relaxation due to bending-mode phonons. The inhomogeneous dephasing time $T_2^*$ is consistent with previous data on hyperfine coupling strength in $^{13}C$ nanotubes.PhysicsOther Research Uni