Atomic, Molecular and Optical Physics Commons^™

Molecular-Frame (E, 2e) Ionization Dynamics Of H2 At High Impact-Energy, Enliang Wang, Esam Ali, Xingyu Li, Xueguang Ren, Xiangjun Chen, Don H. Madison, Alexander Dorn

Physics Faculty Research & Creative Works

Abstract: We report a combined experimental and theoretical study on the electron-impact ionization dynamics of H2 at an impact-energy of 520 eV. The molecular-frame fivefold-differential cross sections were measured for electron emission in the plane perpendicular to the incoming projectile beam. An (e, 2e + ion) triple coincidence method was used covering projectile scattering angles of 6.5°, 10.0° and 20.0° and ejected energies of 20 eV and 30 eV. The experimental cross sections are compared with results from the multi-center distorted-wave (MCDW) as well as the molecular three-body distorted wave (M3DW) approaches. M3DW is in overall better agreement with the …

A Study Of Optical Nonlinearities At The Single-Photon Level For Quantum Logic, Balakrishnan Viswanathan

Graduate Theses and Dissertations

In this dissertation, we shall focus on theoretically studying quantum nonlinear optical schemes to construct a conditional phase gate at the single-photon level. With an aim to develop analytical models, we shall carry out a rigorous quantized multimode field analysis of some of these schemes involving only the interacting field operators. More specifically, we shall first study the three-wave mixing process involving two single-photons in a second-order nonlinear medium (x(2)) under two different cases viz. when the photons are traveling with equal velocities and when they are traveling with different velocities, and explore the possibility of using them for building …

Applications Of The Negatively-Charged Silicon Vacancy Color Center In Diamond, Forrest A. Hubert

Optical Science and Engineering ETDs

The spatial resolution and fluorescence signal amplitude in stimulated emission depletion (STED) microscopy is limited by the photostability of available fluorophores. Here, we show that negatively-charged silicon vacancy (SiV) centers in diamond are promising fluorophores for STED microscopy, owing to their photostable, near-infrared emission and favorable photophysical properties. A home-built pulsed STED microscope was used to image shallow implanted SiV centers in bulk diamond at room temperature. We performed STED microscopy on isolated SiV centers and observed a lateral full-width-at-half-maximum spot size of 89 ± 2 nm, limited by the low available STED laser pulse energy (0.4 nJ). For a …

240— Target Characterization Using Rutherford Backscattering Spectroscopy, Matthew G. Klein, Anthony C. Cooper, Jovahn A. Roumell

GREAT Day Posters

Rutherford backscattering spectroscopy (RBS) is a non-destructive ion-beam analytical technique that is used to determine properties of a target such as thickness, areal density, and elemental composition. This scattering is the result of Coulomb forces between the target atoms and the incident particle. The energy spectrum of the scattered ions depends on the atomic number of the target atoms as well as the target thickness.

Analytical Results For The Three-Body Radiative Attachment Rate Coefficient, With Application To The Positive Antihydrogen Ion H̄+, Jack C. Straton

Physics Faculty Publications and Presentations

To overcome the numerical difficulties inherent in the Maxwell–Boltzmann integral of the velocity-weighted cross section that gives the radiative attachment rate coefficient αRA for producing the negative hydrogen ion H⁻ or its antimatter equivalent, the positive antihydrogen ion H¯⁺ , we found the analytic form for this integral. This procedure is useful for temperatures below 700 K, the region for which the production of H¯⁺ has potential use as an intermediate stage in the cooling of antihydrogen to ultra-cold (sub-mK) temperatures for spectroscopic studies and probing the gravitational interaction of the anti-atom. Our results, utilizing a 50-term …

Mid-Ir Optical Refrigeration And Radiation Balanced Lasers, Saeid Rostami

Optical Science and Engineering ETDs

This dissertation reports recent advances in mid-infrared (mid-IR) optical refrigeration and Radiation Balanced Lasers (RBLs). The first demonstration of optical refrigeration in Ho:YLF and Tm:YLF crystals as promising mid-IR laser cooling candidates is reported. Room temperature laser cooling efficiency of Tm- and Ho-doped crystals at different excitation polarization is measured and their external quantum efficiency and background absorption are extracted. Complete characterization of laser cooling samples is obtained via performing detailed low-temperature spectroscopic analysis, and their minimum achievable temperature as well as conditions to achieve laser cooling efficiency enhancement in mid-IR are investigated. By developing a Thulium-doped fiber amplifier, seeded …

The Breakup Of A Helium Cluster After Removing Attractive Interaction Among A Significant Number Of Atoms In The Cluster, Tao Pang

Physics & Astronomy Faculty Research

The breakup of a quantum liquid droplet is examined through a 4He cluster by removing the attractive tail in the interaction between some of the atoms in the system with the diffusion quantum Monte Carlo simulation. The ground-state energy, kinetic energy, cluster size, and density profile of the cluster are evaluated against the percentage of the atoms without the attractive tail. The condition for the cluster to lose its ability to form a quantum liquid droplet at zero temperature is found and analyzed. The cluster is no longer able to form a quantum liquid droplet when about two-thirds of pairs …

Molecular Spectroscopy: A Study Of Molecules In Earth And Planetary Atmospheres, Mahdi Yousefi Atashgah

Physics Theses & Dissertations

The four most abundant isotopologues (N₂O, ¹⁵NNO, N¹⁵NO, and NN¹⁸O) of nitrous oxide have been measured in the Earth's atmosphere by infrared remote sensing with the Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer. These satellite observations have provided a near global picture of N₂O isotopic fractionation. The relative abundance of the heavier isotopologues increase with altitude and with latitude in the stratosphere as the air becomes older.

Near global 85°S{85°N atmospheric measurement of carbonyl sulfide (OCS), including the minor OC³⁴S and O¹³CS isotopologues, were made by the …

Experimental Determination Of The (0/−) Level For Mg Acceptors In Β-Ga2O3 Crystals, Christopher A. Lenyk, Timothy D. Gustafson, Sergey A. Basun, Larry E. Halliburton, Nancy C. Giles

Faculty Publications

Electron paramagnetic resonance (EPR) is used to experimentally determine the (0/−) level of the Mg acceptor in an Mg-doped β-Ga₂O₃ crystal. Our results place this level 0.65 eV (±0.05 eV) above the valence band, a position closer to the valence band than the predictions of several recent computational studies. The crystal used in this investigation was grown by the Czochralski method and contains large concentrations of Mg acceptors and Ir donors, as well as a small concentration of Fe ions and an even smaller concentration of Cr ions. Below room temperature, illumination with 325 nm laser light …

Questaal: A Package Of Electronic Structure Methods Based On The Linear Muffin-Tin Orbital Technique, Dimitar Pashov, Swagata Acharya, Walter R.L. Lambrecht, Jerome Jackson, Kirill Belashchenko, Athanasios Chantis, Francois Jamet, Mark Van Schilfgaarde

Kirill Belashchenko Publications

This paper summarises the theory and functionality behind Questaal, an open-source suite of codes for calculating the electronic structure and related properties of materials from first principles. The formalism of the linearised muffin-tin orbital (LMTO) method is revisited in detail and developed further by the introduction of short-ranged tight-binding basis functions for full-potential calculations. The LMTO method is presented in both Green's function and wave function formulations for bulk and layered systems. The suite's full-potential LMTO code uses a sophisticated basis and augmentation method that allows an efficient and precise solution to the band problem at different levels of theory, …

Time Dependence Of Few-Body Forster Interactions Among Ultracold Rydberg Atoms, Zhimin Cheryl Liu, Nina P. Inman, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Rubidium Rydberg atoms in either |m_j| sublevel of the 36p_3/2 state can exchange energy via Stark-tuned Förster resonances, including two-, three-, and four-body dipole-dipole interactions. Three-body interactions of this type were first reported and categorized by Faoro et al. [Nat. Commun. 6, 8173 (2015)] and their Borromean nature was confirmed by Tretyakov et al. [Phys. Rev. Lett. 119, 173402 (2017)]. We report the time dependence of the N-body Förster resonance N×36p_3/2,|mj|=1/2→36s_1/2+37s_1/2+(N−2)×36p_3/2,|mj|=3/2, for N=2, 3, …

Perturbed Field Ionization For Improved State Selectivity, Vincent C. Gregoric, Jason Bennett, Bianca R. Gualtieri, Hannah P. Hastings, Ankitha Kannad, Zhimin Cheryl Liu, Maia R. Rabinowitz, Zoe A. Rowley, Maio Wang, Lauren Yoast, Thomas J. Carroll, Michael W. Noel

Physics and Astronomy Faculty Publications

Selective field ionization (SFI) is used to determine the state or distribution of states to which a Rydberg atom is excited. By evolving a small perturbation to the ramped electric field using a genetic algorithm, the shape of the time-resolved ionization signal can be controlled. This allows for the separation of signals from pairs of states that would be indistinguishable with unperturbed SFI. Measurements and calculations are presented that demonstrate this technique and shed light on how the perturbation directs the pathway of the electron to ionization. Pseudocode for the genetic algorithm is provided. Using the improved resolution afforded by …

The Emergence Of The Local Moment Molecular Spin Transistor, Guanhua Hao, Ruihua Cheng, Peter Dowben

Peter Dowben Publications

Local moment molecular systems have now been used as the conduction channel in gated spintronics devices, and some of these three terminal devices might even be considered molecular spin transistors. In these systems, the gate voltage can be used to tune the molecular level alignment, while applied magnetic fields have an influence on the spin state, altering the magnetic properties, and providing insights to the magnetic anisotropy. More recently, the use of molecular spin crossover complexes, as the conduction channel, has led to devices that are both nonvolatile and have functionality at higher temperatures. Indeed, some devices have now been …

Characterization Of A Trochoidal Electron Monochromator, Jesse Kruse

Honors Program: Senior Projects (Public)

This thesis presents a quantitative study of a trochoidal electron monochromator and attempts to observe the 2p^53p^2 resonance in neon. A detailed description of the experimental apparatus, including the electron beam system, the vacuum system, and the light analysis system, is presented first. Then, we discuss the theory of how the electron beam is monochromatized, how we measured monochomatization, and how we analyze the light being emitted from the collision cell. The light analysis system is capable of accurately measuring the relative Stokes parameters for any polarization of light, and the electron beam system is capable of producing electron beams …

Probing Ferroelectricity By X-Ray Absorption Spectroscopy In Molecular Crystals, Fujie Tang, Xuanyuan Jiang, Hsin Yu Ko, Jianhang Xu, Mehmet Topsakal, Guanhua Hao, Alpha T. N'Diaye, Peter Dowben, Deyu Lu, Xiaoshan Xu, Xifan Wu

Peter Dowben Publications

We carry out X-ray absorption spectroscopy experiment at the oxygen K edge in croconic acid (C₅H₂O₅) crystal as a prototype of ferroelectric organic molecular solid, whose electric polarization is generated by proton transfer. The experimental spectrum is well reproduced by the electron-hole excitation theory simulations from configuration generated by ab initio molecular dynamics simulation. When inversion symmetry is broken in the ferroelectric state, the hydrogen bonding environment on the two bonded molecules become inequivalent. Such a difference is sensitively probed by the bound excitation in the pre-edge, which is strongly localized on the excited …

Measurement Of The 160Gd(P,N)160Tb Excitation Function From 4 18 Mev, Using A Stacked Foil Technique, Ryan K. Chapman

Theses and Dissertations

A stack of thin Gd, Ti, and Cu foils were irradiated with an 18 MeV proton beam at Lawrence-Berkeley National Laboratory's 88-Inch Cyclotron to investigate the ¹⁶⁰Gd(p,n)¹⁶⁰Tb nuclear reaction for nuclear forensics applications. This experiment will improve knowledge of ¹⁶⁰Tb production rates, allowing ¹⁶⁰Tb to be efficiently created in a foil stack consisting of other proton induced isotopes for forensics applications. A set of 15 measured cross sections between 4-18 MeV for ¹⁶⁰Gd(p,n)¹⁶⁰Tb were obtained using a stacked foil technique. The foil stack consisted of one stainless steel, one iron, fifteen gadolinium, …

The Design Of A Continuous Wave Molecular Nitrogen Stimulated Raman Laser In The Visible Spectrum, Timothy J. Bate

Theses and Dissertations

Hollow-core photonic crystal fibers (HCPCFs) shows promise as a hybrid laser with higher nonlinear process limits and small beam size over long gain lengths. This work focuses on the design of a CW molecular nitrogen (N₂) stimulated Raman laser. N₂ offers Raman gains scaling up to 900 amg, scaling higher than H₂. The cavity experiment showed the need to include Rayleigh scattering in the high pressure required for N₂ Raman lasing. Even at relatively low pressure ssuch as 1,500 psi, high conversion percentages should be found if the fiber length is chosen based on …

Pulsed Laser Generation In S+/S Band Using Thulium Fluoride Fiber With Saturable Absorber, Reduan Siti Aisyah

Student Works (2020-2029)

Demands on photonic applications has become highly saturated in C-band and L-band region, forcing the needs to work in S band region for the development of alternative data network and photonics technology tools to fulfill the future needs. There are only a few reports on exploiting S band fiber laser operation which mainly used depressed-cladding erbium-doped fiber (DC-EDF) as gain medium. The region covers only ~1480 nm to 1510 nm as mentioned by previous works. Other than that, there is limitation in the selection of rare-element gain medium to generate the emission in S band region. The use of thulium-fluoride …

Near-Infrared-Sensitive Photorefractive Sn2P2S6 Crystals Grown By The Bridgman Method, O. M. Shumelyuk, A. Y. Volkov, Y. Skrypka, Larry E. Halliburton, Nancy C. Giles, Christopher A. Lenyk, Sergey A. Basun, A. A. Grabar, Y. M. Vysochansky, S. G. Odoulov, D. R. Evans

Faculty Publications

Ferroelectric tin hypothiodiphosphate (Sn₂P₂S₆) crystals are well-known for their significant piezoelectric, electro-optic, and nonlinear optical properties. These crystals have usually been grown by a vapor transport technique. We report in this paper on the first study of photorefractive nonlinearity in Sn₂P₂S₆ crystals grown by the Bridgman method. Pronounced photorefraction is observed in the near-infrared region of the spectrum even with no preliminary optical sensitizing.

Rapid Analysis Of Plutonium Surrogate Material Via Hand-Held Laser-Induced Breakdown Spectroscopy, Ashwin P. Rao

Theses and Dissertations

This work investigated the capability of a portable LIBS device to detect and quantify dopants in plutonium surrogate alloys, specifically gallium, which is a common stabilizer used in plutonium alloys. The SciAps Z500-ER was utilized to collect spectral data from cerium-gallium alloys of varying gallium concentrations. Calibration models were built to process spectra from the Ce-Ga alloys and calculate gallium concentration from spectral emission intensities. Univariate and multivariate analysis techniques were used to determine limits of detection of different emission line ratios. Spatial mapping measurements were conducted to determine the device's ability to detect variations in gallium concentration on the …