Astrophysics and Astronomy Commons^™

The [Cii] 158ΜM Line Emission In High-Redshift Galaxies, Guilaine Lagache, Morgane Cousin, Marios Chatzikos

Physics and Astronomy Faculty Publications

Gas is a crucial component of galaxies, providing the fuel to form stars, and it is impossible to understand the evolution of galaxies without knowing their gas properties. The [CII] fine structure transition at 158 μm is the dominant cooling line of cool interstellar gas, and is the brightest of emission lines from star forming galaxies from FIR through metre wavelengths, almost unaffected by attenuation. With the advent of ALMA and NOEMA, capable of detecting [CII]-line emission in high-redshift galaxies, there has been a growing interest in using the [CII] line as a probe of the physical conditions of …

Spatially Resolved Dust, Gas, And Star Formation In The Dwarf Magellanic Irregular Ngc 4449, D. Calzetti, G W. Wilson, B. T. Draine, H. Roussel, K. E. Johnson, M. H. Heyer, W. F. Wall, K. Grasha, A. Battisti, J. E. Andrews, A. Kirkpatrick, D. Rosa González, O. Vega, J. Puschnig, M. Yun, G. Östlin, A. S. Evans, Y. Tang, James Lowenthal, D. Sánchez-Arguelles

Astronomy: Faculty Publications

We investigate the relation between gas and star formation in subgalactic regions, ˜360 pc to ˜1.5 kpc in size, within the nearby starburst dwarf NGC 4449, in order to separate the underlying relation from the effects of sampling at varying spatial scales. Dust and gas mass surface densities are derived by combining new observations at 1.1 mm, obtained with the AzTEC instrument on the Large Millimeter Telescope, with archival infrared images in the range 8-500 μm from the Spitzer Space Telescope and the Herschel Space Observatory. We extend the dynamic range of our millimeter (and dust) maps at the faint …

Automated Data Processing Architecture For The Gemini Planet Imager Exoplanet Survey, Jason J. Wang, Marshall D. Perrin, Dmitry Savransky, Pauline Arriaga, Jeffrey K. Chilcote, Robert J. De Rosa, Maxwell A. Millar-Blanchaer, Christian Marois, Julien Rameau, Schuyler G. Wolff, Jacob Shapiro, Jean Baptiste Ruffio, Jérôme Maire, Franck Marchis, James R. Graham, Bruce Macintosh, S. Mark Ammons, Vanessa P. Bailey, Travis S. Barman, Sebastian Bruzzone, Joanna Bulger, Tara Cotton, René Doyon, Gaspard Duchêne, Michael P. Fitzgerald, Katherine B. Follette, Stephen Goodsell, Alexandra Z. Greenbaum, Pascale Hibon, Li Wei Hung, Patrick Ingraham, Paul Kalas, Kimberly Ward-Duong, Et Al

Astronomy: Faculty Publications

The Gemini Planet Imager Exoplanet Survey (GPIES) is a multiyear direct imaging survey of 600 stars to discover and characterize young Jovian exoplanets and their environments. We have developed an automated data architecture to process and index all data related to the survey uniformly. An automated and flexible data processing framework, which we term the Data Cruncher, combines multiple data reduction pipelines (DRPs) together to process all spectroscopic, polarimetric, and calibration data taken with GPIES. With no human intervention, fully reduced and calibrated data products are available less than an hour after the data are taken to expedite follow up …

Galaxy And Mass Assembly (Gama): The Consistency Of Gama And Wise Derived Mass-To-Light Ratios, T. Kettlety, J. Hesling, S. Phillipps, M. N. Bremer, M. E. Cluver, E. N. Taylor, J. Bland-Hawthorn, S. Brough, R. De Propris, S. P. Driver, Benne W. Holwerda, L. S. Kelvin, W. Sutherland, A. H. Wright

Faculty and Staff Scholarship

Recent work has suggested that mid-IR wavelengths are optimal for estimating the mass-to-light ratios of stellar populations and hence the stellar masses of galaxies. We compare stellar masses deduced from spectral energy distribution (SED) models, fitted to multiwavelength optical-NIR photometry, to luminosities derived from WISE photometry in the W1 and W2 bands at 3.6 and 4.5 μmfor non-star forming galaxies. The SED-derived masses for a carefully selected sample of low-redshift (z≤0.15) passive galaxies agree with the prediction from stellar population synthesis models such that M*/LW1 ≃0.6 for all such galaxies, independent of other stellar population parameters. The small scatter between …

Herschel Observations Of Edge-On Spirals (Heroes) Iv. Dust Energy Balance Problem, Aleksandr V. Mosenkov, Flor Allaert, Maarten Baes, Simone Bianchi, Peter Camps, Christopher J.R. Clark, Marjorie Decleir, Gert De Geyter, Ilse De Looze, Jacopo Fritz, Gianfranco Gentile, Benne W. Holwerda, Thomas M. Hughes, Fraser Lewis, Matthew W.L. Smith, Joris Verstappen, Sam Verstocken, Sébastien Viaene

Faculty and Staff Scholarship

We present results of the detailed dust energy balance study for the seven large edge-on galaxies in the HEROES sample using three-dimensional (3D) radiative transfer (RT) modelling. Based on available optical and near-infrared (NIR) observations of the HEROES galaxies, we derive the 3D distribution of stars and dust in these galaxies. For the sake of uniformity, we apply the same technique to retrieve galaxy properties for the entire sample: we use a stellar model consisting of a Sérsic bulge and three double-exponential discs (a superthin disc for a young stellar population and thin and thick discs for old populations). For …

Climate Modeling, Outgoing Longwave Radiation, And Tropical Cyclone Forecasting, Thomas Rechtman

Honors Undergraduate Theses

Climate modeling and tropical cyclone forecasting are two significant is- sues that are continuously being improved upon for more accurate weather forecasting and preparedness. In this thesis, we have studied three climate models and formulated a new model with a view to determine the outgoing longwave radiation (OLR) budget at the top of the atmosphere (TOA) as ob- served by the National Oceanic and Atmospheric Administration’s (NOAA) satellite based Advanced Very High Resolution Radiometer (AVHRR). In 2006, Karnauskas proposed the African meridional OLR as an Atlantic hur- ricane predictor, the relation was further proven in 2016 by Karnauskas and Li …

Foreword By Guest Editors Maa 2018 Volume 18 Issue 4, Frank Prendergast, A. César González-García, Gary Wells, Juan Antonio Belmonte

Conference Papers

MAA SPECIAL ISSUE VOL 18 ISSUE 4:

Sixty-three (63) Selected (peer reviewed) Papers of the INSAP X – Oxford XI – SEAC 25th Joint Conference ‘ROAD TO THE STARS’, held in Santiago de Compostela, Spain, 18th–22nd September 2017

Mediterranean Archaeology and Archaeometry (MAA) is an Open Access Journal published since 2001 by The University of the Aegean, Department of Mediterranean Studies, Rhodes, Greece.

It covers the dual nature of archaeology and cultural heritage with science which includes, amongst others, natural science applied to archaeology (physics, chemistry, biology, geology, geophysics, astronomy), archaeology, ancient history, cultural sustainability, astronomy in culture, physical anthropology, …

Solar Alignment And The Irish Passage Tomb Tradition, Frank Prendergast

Book/Book Chapter

A succinct and very useful, illustrated, explanatory guide to the phenomenon of solar alignment in the irish Passage Tomb tradition. Includes a listing of where to visit the 15 known astronomically aligned passage tombs in the 32 counties.

Written by Dr Frank Prendergast who is now Emeritus at the Dublin Institute of Technology, where he researches Irish prehistoric monuments and their landscapes from a cultural astronomy perspective. His current interests and publications are on the meaning of the dark sky in the prehistoric past and on the conservation of archaeological landscapes from light pollution.

Heritage Guides are included free with …

Groundwater Withdrawals Under Drought: Reconciling Grace And Land Surface Models In The United States High Plains Aquifer, Wanshu Nie, Benjamin Zaitchik, Matthew Rodell, Sujay V. Kumar, Martha C. Anderson, Christopher Hain

United States National Aeronautics and Space Administration: Publications

Advanced Land Surface Models (LSM) offer a powerful tool for studying hydrological variability. Highly managed systems, however, present a challenge for these models, which typically have simplified or incomplete representations of human water use. Here we examine recent groundwater declines in the US High Plains Aquifer (HPA), a region that is heavily utilized for irrigation and that is also affected by episodic drought. To understand observed decline in groundwater and terrestrial water storage during a recent multiyear drought, we modify the Noah-MP LSM to include a groundwater irrigation scheme. To account for seasonal and interannual variability in active irrigated area, …

Two Decades Old Entropy Stable Method For The Euler Equations Revisited, Björn Sjögreen, H. C. Yee

United States National Aeronautics and Space Administration: Publications

The two decades old high order central differencing via entropy splitting and summation-by-parts (SBP) difference closure of Olsson and Oliger, Gerritsen and Olsson, and Yee et al. [2, 7, 25] is revisited. The entropy splitting is a form of skewsymmetric splitting in terms of the physical entropy of the nonlinear Euler flux derivatives. Central differencing applied to the entropy splitting form of the Euler flux derivatives together with SBP difference operators will, hereafter, be referred to as entropy split schemes.

The Leech Exoplanet Imaging Survey: Limits On Planet Occurrence Rates Under Conservative Assumptions, Jordan M. Stone, Andrew J. Skemer, Philip M. Hinz, Mariangela Bonavita, Kaitlin M. Kratter, Anne Lise Maire, Denis Defrere, Vanessa P. Bailey, Eckhart Spalding, Jarron M. Leisenring, S. Desidera, M. Bonnefoy, Beth Biller, Charles E. Woodward, Th Henning, Michael F. Skrutskie, J. A. Eisner, Justin R. Crepp, Jennifer Patience, Gerd Weigelt, Robert J. De Rosa, Joshua Schlieder, Wolfgang Brandner, Dániel Apai, Kate Su, Steve Ertel, Kimberly Ward-Duong, Katie M. Morzinski, Dieter Schertl, Karl Heinz Hofmann, Laird M. Close, Stefan S. Brems

Astronomy: Faculty Publications

We present the results of the largest L' (3.8 μm) direct imaging survey for exoplanets to date, the Large Binocular Telescope Interferometer Exozodi Exoplanet Common Hunt (LEECH). We observed 98 stars with spectral types from B to M. Cool planets emit a larger share of their flux in L' compared to shorter wavelengths, affording LEECH an advantage in detecting low-mass, old, and cold-start giant planets. We emphasize proximity over youth in our target selection, probing physical separations smaller than other direct imaging surveys. For FGK stars, LEECH outperforms many previous studies, placing tighter constraints on the hot-start planet occurrence frequency …

Relationship Between Interplanetary Conditions And Changes In The Geomagnetic Field To Understand The Causes Of Geomagnetically Induced Currents, Cameron P. Maillet

Honors Theses and Capstones

Geomagnetically Induced Currents (GICs) are electrical currents induced in ground-level conductive networks, like power lines and pipelines, which can cause costly damage to infrastructure. GICs are induced in response to fast changes in the geomagnetic field (GMF) according to Faraday’s Law of Electromagnetic Induction. The purpose of this study was to identify the parameters of the solar wind and interplanetary shocks which are most strongly correlated with large, fast changes in the magnitude of the GMF. GMF data is 1-min averaged time series of mid- and high-latitude magnetometer measurements in the Sym/H and AL indices, respectively. For solar wind data, …

Observations Of Ion Density And Temperature Around The International Space Station During Two Geomagnetic Storms, Alex M. Wright

Honors Theses and Capstones

The International Space Station (ISS) is a low Earth orbit research facility and host to an international crew. Geomagnetic storms cause changes in the Earth’s magnetic field and affect the ion density and temperature in the ionosphere which could pose a hazard to ISS crew. This hazard is measured by the Floating Potential Measurement Unit (FPMU) which measures ion density, ion temperature, and the charge differential of the ISS relative to its surrounding environment. I analyzed data collected by Narrow Sweep Langmuir Probe for two storms in 2015. Ion density and temperature were affected by geomagnetic storms, but the effects …

Spectrally-Selective Energy-Harvesting Solar Windows For Public Infrastructure Applications, Mikhail Vasiliev, Kamal Alameh, Mohammad Alam

Research outputs 2014 to 2021

A study of photovoltaic solar window technologies is reported and it focuses on their structural features, functional materials, system development, and suitability for use in practical field applications including public infrastructures and agricultural installations. Energy generation performance characteristics are summarized and compared to theory-limit predictions. Working examples of pilot-trial solar window-based installations are described. We also report on achieving electric power outputs of about 25 Wp/m2 from clear and transparent large-area glass-based solar windows.

Determining The Small-Scale Structure And Particle Properties In Saturn's Rings From Stellar And Radio Occultations, Richard Jerousek

Electronic Theses and Dissertations

Saturn's rings consist of icy particles of various sizes ranging from millimeters to several meters. Particles may aggregate into ephemeral elongated clumps known as self-gravity wakes in regions where the surface mass density and epicyclic frequency give a Toomre critical wavelength which is much larger than the largest individual particles (Julian and Toomre 1966). Optical depth measurements at different wavelengths can be used to constrain the sizes of individual particles (Zebker et al. 1985, Marouf et al. 1983) while measurements of optical depths spanning many viewing geometries can be used to determine the properties of self-gravity wakes (Colwell et al. …

Single-Site Catalyst Promoters Accelerate Metal- Catalyzed Nitroarene Hydrogenation, Liang Wang, Erjia Guan, Jian Zhang, Junhao Yang, Yihan Zhu, Yu Han, Ming Yang, Cheng Cen, Gang Fu, Bruce C. Gates, Feng-Shou Xiao

Faculty & Staff Scholarship

Atomically dispersed supported metal catalysts are drawing wide attention because of the opportunities they offer for new catalytic properties combined with efficient use of the metals. We extend this class of materials to catalysts that incorporate atomically dispersed metal atoms as promoters. The catalysts are used for the challenging nitroarene hydro- genation and found to have both high activity and selectivity. The promoters are single-site Sn on TiO2 supports that incorporate metal nanoparticle catalysts. Represented as M/Sn- TiO2 (M = Au, Ru, Pt, Ni), these catalysts decidedly outperform the unpromoted supported metals, even for hydrogenation of nitroarenes substituted with various …

Correlation Between Emission Lines And Radio Luminosities Of Active Galactic Nuclei, Jessica Short-Long

Theses and Dissertations--Physics and Astronomy

Radio-loud active galactic nuclei (AGN) are one class of objects associated with accretion activity onto supermassive black holes in centers of massive galaxies. They are believed to be in a radiatively-inefficient accretion mode with low accretion rate. To understand this accretion mode, it is important to measure its radiative output at high energies (> 13.6eV), which can be traced through optical emission lines. However, little is known about their true radiative output. This is because no correlation between optical emission-line and radio luminosity has been found for the majority of low-luminosity radio AGN, which are often classified as low-excitation radio …

Differentiation In Impact Melt Sheets As A Mechanism To Produce Evolved Magmas On Mars, Ari Koeppel

Dissertations and Theses

Asteroid bombardment contributed to extensive melting and resurfacing of ancient (> 3 Ga) Mars, thereby influencing the early evolution of the Martian crust. However, information about how impact melting has altered Mars’ crustal petrology is limited. Evidence from some of the largest impact structures on Earth, such as Sudbury and Manicouagan, suggests that some impact melt sheets experience chemical differentiation. If these processes occur on Mars, we expect to observe differentiated igneous materials in some exhumed rock samples. Some rocks observed in Gale crater are enriched in alkalis (up to 14 wt% Na₂O + K₂O) and …

Study Of The Cygnus Region With Fermi And Hawc, Andrew Robare

Dissertations, Master's Theses and Master's Reports

The Cygnus Cocoon is an extended source of high-energy gamma-ray emission in the Cygnus region. The gamma-ray emission has been attributed to a volume 50pc in diameter of freshly-accelerated particles near the Supernova Remnant γ Cygni which is located 1.4kpc from the solar system [Ackermann et al., 2011], [Tibaldo et al., 2013]. Since its discovery in 2011, Fermi LAT has improved their event reconstruction to allow analysis at higher energies, and recorded six additional years of data. An analysis was performed on the entire dataset to reproduce the previous results, then expand on them with higher energies and larger time …

Evaluating The Effectiveness Of Current Atmospheric Refraction Models In Predicting Sunrise And Sunset Times, Teresa Wilson

Dissertations, Master's Theses and Master's Reports

The standard value for atmospheric refraction on the horizon of 34', used in all publicly available sunrise and sunset calculators, is found to be inadequate. The assumptions behind atmospheric models that predict this value fail to account for real meteorological conditions. The result is an uncertainty of one to five minutes in sunrise and sunset predictions at mid-latitudes (0° - 55° N/S). A sunrise/set calculator that interchanges the refraction component by varying the refraction model was developed. Two atmospheric refraction models of increasing complexity were tested along with the standard value. The predictions were compared with data sets of observed …

Effects Of Mass And Distance Uncertainties On Calculations Of Flux From Giant Molecular Clouds, Matt Coel

Dissertations, Master's Theses and Master's Reports

It is assumed that the distribution of the Milky Way cosmic rays, the cosmic ray ‘sea,’ is even throughout the Galaxy. This assumption can be tested by measuring gamma rays produced from cosmic ray interactions with Giant Molecular Clouds. The gamma ray flux depends on the mass and distance of a given molecular cloud as well as the cosmic ray flux in its vicinity. Thus a predicted gamma ray flux can be compared to actual flux data from a detector. Uncertainties from measuring the mass of and distance to the clouds are taken into account for this prediction. This report …

Compositional And Topographical Characterization Of Carbonaceous Chondritic Meteorites Moss And Murray Using Micro-Raman Spectroscopy And Sem/Eds, Aaron Stokke

All Graduate Theses, Dissertations, and Other Capstone Projects

Carbonaceous chondritic meteorites are considered some of the most primitive surviving materials from the formation of our solar system. Thus, these objects can provide information about planet formation through their physical properties (such as structure, composition, and morphology) which can be characterized using microscopy and spectroscopy techniques. In this work, the analytical methods of Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and optical microscopy are applied to determine the mineralogical, topographical, and elemental compositions of two carbonaceous chondritic fragments: Moss and Murray. Both samples were comprised of chondrules and matrix while Moss contained chondrule rims and Murray …

Whole Earth Telescope Discovery Of A Strongly Distorted Quadrupole Pulsation In The Largest Amplitude Rapidly Oscillating Ap Star, Daniel L. Holdsworth, Donald W. Kurtz, Hideyuki Saio, Judith L. Provençal, Bruno Letarte, Ramotholo R. Sefako, Véronique Petit, Barry Smalley, H. Thomsen, C. L. Fletcher

Aerospace, Physics, and Space Science Faculty Publications

We present a new analysis of the rapidly oscillating Ap (roAp) star, 2MASS J19400781 - 4420093 (J1940; V = 13.1). The star was discovered using SuperWASP broad-band photometry to have a frequency of 176.39 d-1 (2041.55 μHz; P = 8.2min; Holdsworth et al. 2014a) and is shown here to have a peak-to-peak amplitude of 34 mmag. J1940 has been observed during three seasons at the South African Astronomical Observatory, and has been the target of a Whole Earth Telescope campaign. The observations reveal that J1940 pulsates in a distorted quadrupole mode with unusual pulsational phase variations. A higher signal-to-noise ratio …

Prompt Photon-Jet Angular Correlations At Central Rapidities In P + A Collisions, Sanjin Benić, Adrian Dumitru

Publications and Research

Photon-jet azimuthal correlations in proton-nucleus collisions are a promising tool for gaining information on the gluon distribution of the nucleus in the regime of nonlinear color fields. We compute such correlations from the process $g → q\bar{q}γ$ in the rapidity regime where both the projectile and target light-cone momentum fractions are small. By integrating over the phase space of the quark which emits the photon, subject to the restriction that the photon picks up most of the transverse momentum (to pass an isolation cut), we effectively obtain a g + A → qγ process. For nearly back-to-back photon-jet configurations we …

Reconstructing Phase Diagrams From Local Measurements Via Gaussian Processes: Mapping The Temperature-Composition Space To Confidence, Dhiren K. Pradhan, Shalini Kumari, Evgheni Strelcov, Dillip K. Pradhan, Ram S. Katiyar, Sergei V. Kalinin, Nouamane Laanait, Rama K. Vasudevan

Faculty & Staff Scholarship

We show the ability to map the phase diagram of a relaxor-ferroelectric system as a function of temperature and composition through local hysteresis curve acquisition, with the voltage spectroscopy data being used as a proxy for the (unknown) microscopic state or thermodynamic parameters of materials. Given the discrete nature of the measurement points, we use Gaussian processes to reconstruct hysteresis loops in temperature and voltage space, and compare the results with the raw data and bulk dielectric spectroscopy measurements. The results indicate that the surface transition temperature is similar for all but one composition with respect to the bulk. Through …

Cavitons And Spontaneous Hot Flow Anomalies In A Hybrid-Vlasov Global Magnetospheric Simulation, Xochitl Blanco-Cano, Markus Battarbee, Lucile Turc, Andrew P. Dimmock, Emilia K.J. Kilpua, Sanni Hoilijoki, Urs Ganse, David G. Sibeck, Paul A. Cassak, Robert C. Fear, Riku Jarvinen, Liisa Juusola, Yann Pfau-Kempf, Rami Vainio, Minna Palmroth

Faculty & Staff Scholarship

Abstract. In this paper we present the first identification of foreshock cavitons and the formation of spontaneous hot flow anomalies (SHFAs) with the Vlasiator global magne- tospheric hybrid-Vlasov simulation code. In agreement with previous studies we show that cavitons evolve into SHFAs. In the presented run, this occurs very near the bow shock. We report on SHFAs surviving the shock crossing into the down- stream region and show that the interaction of SHFAs with the bow shock can lead to the formation of a magnetosheath cavity, previously identified in observations and simulations. We report on the first identification of long-term …

Isoscalar Ππ; Kk; Ηη Scattering And The Σ; F0; F2 Mesons From Qcd, Raul A. Briceño, Jozef J. Dudek, Robert G. Edwards, David J. Wilson

Physics Faculty Publications

We present the first lattice QCD study of coupled isoscalar ππ;K ¯K; ηη S- and D-wave scattering extracted from discrete finite-volume spectra computed on lattices which have a value of the light quark mass corresponding to m_π ∼ 391 MeV. In the J^P = 0⁺ sector we find analogues of the experimental σ and f₀ (980) states, where the σ appears as a stable bound-state below ππ threshold, and, similar to what is seen in experiment, the f₀ (980) manifests itself as a dip in the ππ cross section in the vicinity of the …

Electrostatic Potential And Valence Modulation In La0.7sr0.3mno3 Thin Films, Robbyn Trappen, A. C. Garcia- Castro, Vu Thanh Tra, Chih-Yeh Huang, Wilfredo Ibarra-Hernandez, James Fitch, Sobhit Singh, Jingling Zhou, Guerau Cabrera, Ying-Hao Chu, James M. Lebeau, Aldo H. Romero, Mikel B. Holcomb

Faculty & Staff Scholarship

The Mn valence in thin film La0.7Sr0.3MnO3 was studied as a function of film thickness in the range of 1–16 unit cells with a combination of non-destructive bulk and surface sensitive X-ray absorption spectroscopy techniques. Using a layer-by-layer valence model, it was found that while the bulk averaged valence hovers around its expected value of 3.3, a significant deviation occurs within several unit cells of the surface and interface. These results were supported by first principles calculations. The surface valence increases to up to Mn3.7+, whereas the interface valence reduces down to Mn2.5+. The change in valence from the expected …

Electron Paramagnetic Resonance And Optical Absorption Study Of Acceptors In Cdsip2 Crystals, E M. Scherrer, L E. Halliburton, E M. Golden, K T. Zawilski, P G. Schunemann, F K. Hopkins, K L. Averett, N C. Giles

Faculty & Staff Scholarship

Cadmium silicon diphosphide (CdSiP2) is a nonlinear material often used in optical parametric oscillators (OPOs) to produce tunable laser output in the mid-infrared. Absorption bands associated with donors and acceptors may overlap the pump wave- length and adversely affect the performance of these OPOs. In the present investigation, electron paramagnetic resonance (EPR) is used to identify two unintentionally present acceptors in large CdSiP2 crystals. These are an intrinsic silicon-on-phosphorus anti- site and a copper impurity substituting for cadmium. When exposed to 633 nm laser light at temperatures near or below 80 K, they convert to their neutral paramagnetic charge states …

Enhanced Hot Electron Lifetimes In Quantum Wells With Inhibited Phonon Coupling, Hamidreza Esmaielpour, Vincent R. Whiteside, Herath P. Piyathilaka, Sangeetha Vijeyaragunathan, Bin Wang, Echo Adcock-Smith, Kenneth P. Roberts, Tetsuya D. Mishima, Michael B. Santos, Alan D. Bristow, Ian R. Sellers

Faculty & Staff Scholarship

Hot electrons established by the absorption of high-energy photons typically thermalize on a picosecond time scale in a semiconductor, dissipating energy via various phonon-mediated relaxation pathways. Here it is shown that a strong hot carrier distribution can be produced using a type-II quantum well structure. In such systems it is shown that the dominant hot carrier thermalization process is limited by the radiative recombination lifetime of electrons with reduced wavefunction overlap with holes. It is proposed that the subsequent reabsorption of acoustic and optical phonons is facilitated by a mismatch in phonon dispersions at the InAs-AlAsSb interface and serves to …