Mark Zammit, "Colliding particles and their applications," Friday, Dec 2
Los Alamos National Laboratory
ABSTRACT: Chemical reactions are the basis of life, and accurately describing chemical reactions is thus of great importance to science and has major implications in innovation, industry and medicine. Collisions between electrons, atoms and molecules underlie these chemical reactions. However, after many decades and attempts, predictions of what happens during these collisions (involving molecules) have remained quantitatively inconsistent with measurements and the problem was largely unsolved.
To tackle this problem, researchers at Los Alamos National Laboratory and Curtin University in Australia have developed “the convergent close-coupling code” (CCC), to model the simplest collisions between electrons, positrons (anti-electrons), atoms and molecules. Starting from the first principles of Quantum Mechanics and utilizing super computers, the program very accurately calculates the probability of collision processes such as the ionization or excitation of a molecule.
To date the method has been applied to positron and electron scattering from molecular hydrogen H2 and electron (e-) scattering from the constituents of fusion plasmas: H2, its ions H2+ and the ions isotopologues. Results from these studies are in good agreement with experiments and will have direct implications in the modeling of fusion plasmas, design of aerospace materials (for atmospheric entry), astrophysics and atmospheric modeling. In this talk, I will describe the CCC method, present some recent results and discuss opportunities afforded to young researchers.
Daniel Slaughter, "Bond-selective chemistry with low-energy electrons," Friday, Nov 4
Lawrence Berkley National Laboratory
ABSTRACT: Anion momentum imaging experiments are combined with electron scattering calculations to investigate the dynamics of dissociative electron attachment in isolated molecules. Electronic Feshbach resonances typically play a central role in dissociative electron attachment. In these resonances, a valence electron is excited to an unoccupied orbital and the incident electron is captured in the same orbital. For the case of methane, one triply-degenerate Feshbach resonance undergoes Jahn-Teller splitting through molecular distortions, leading to four observed final states, each having a 2-body and a 3-body dissociation with anionic products H- and CH2- andneutrals CH3, CH2, H2 or H. In ammonia, one resonance leads to H- + NH2 and NH2- + H, the latter resulting from non-adiabatic charge transfer. A higher energy resonance leads directly to H- and electronically excited NH2 and indirectly to NH2-. The dynamics of damage of isolated DNA and RNA bases by resonant low energy electrons will also be discussed.
Dragos Anghel, "Electron-phonon Interaction in Nanostructures at sub-Kelvin Temperatures," Wednesday, Nov 2
Horia Hulubei National Institute for Physics and Nuclear Engineering
ABSTRACT: Ultrasensitive nanoscopic detectors for electromagnetic radiation consist of thin metallic films deposited on dielectric membranes. The metallic films, of thickness d, of the order of 10 nm, form the thermal sensing element (TSE), which absorbs the incident radiation and measures its power flux or the photons’ energy. To achieve the sensitivity required for space born astronomical observations, the TSE works at temperatures of the order of 0.1 K. The dielectric membranes are used for the thermal insulation of the TSE and are of thickness of the order of 100 nm. In such conditions, the phonon gas in the detector assumes a quasi-two-dimensional distribution, whereas quantization of the electrons wavenumbers in the direction perpendicular to the film surfaces lead to the formation of quasi two-dimensional electronic sub-bands.
We analyze the heat power, P, between electrons and phonons at temperatures below 0.2 K, in detectors structures of such thicknesses. If we denote by Te the electron's temperature and by Tph the phonons temperature, we can write P ≡ P(0)(Te)-P(1)(Te,Tph); P(0) is the power “emitted” by the electron system to the phonons and P(1) is the power “absorbed” by the electrons from the phonons. Due to the quantization of the electronic states and the quasi-two-dimensional distribution of the phonon gas, P(d, Te) and P(d,Tph) show very strong oscillations with d, forming sharp crests almost parallel to the temperature axes. In the valleys between the crests, P ∝ T3.5e - T3.5ph. From valley to crest, P increases by more than one order of magnitude and on the crests P does not have a simple power law dependence on temperature.
The strong modulation of P with the thickness of the film may provide a way to control the electron-phonon heat power and the power dissipation in thin metallic films. Eventually the same mechanism may be used to detect small variations of d or surface contamination.
Chris Griffo, "Roles of an Optical Engineer at Celestron," Friday, Oct 28
ABSTRACT: Amateur astronomy wouldn’t be what it is today without the advancement of some key technologies that have been developed by Celestron, such as the mass manufacturing of high quality Schmidt correctors. As an Optical Engineer, knowledge of physics and other engineering disciplines are crucial in the development of these technologies. In this presentation I will give a quick introduction into telescope design, the Schmidt corrector/camera, history of Celestron, key roles of an optical engineer and some of the new products Celestron has introduced. Along with these topics, I will also go into my path through the optics industry and steps I took before and after I graduated from the CSU Fullerton Physics Department.
Lee Lindbolm, "Neutron Stars: Where Gravitation Theory Meets Nuclear Physics," Friday, Oct 14
UC San Diego
ABSTRACT: Neutron stars are created by the gravitational collapse of massive stars that have exhausted their nuclear fuel. The bulk of the material in these stars is compressed to densities larger than those in the nuclei of normal atoms. Their gravitational fields become nearly as strong as those at the surfaces of black holes. In this talk I will explore some of the things we can learn about nuclear physics by applying our knowledge of gravitation theory to astronomical observations of these stars.
Qing Ryan, "Physics Problem Solving: Customizable Computer Coaches for Physics Online (C3PO)," Friday, Sept 30
Cal Poly Pomona
ABSTRACT: Problem solving skill is highly valued by employers and educators. Since introductory physics is a pre-requisite for nearly all science and engineering majors, it is an ideal gateway to teach problem solving. In this talk, I will introduce a set of computer programs that were developed to help students become better problem solvers by coaching them in the use of an expert-like framework. There are three parts to this talk: Pedagogical design of the computer coaches, Assessments, and Next generation coaches. These computer coaches are assessed from following aspects: Usage and usability, Usefulness perceived by students, and Educational impact on problem solving.
Brandon Eberly, "Searching for sterile neutrinos with MicroBooNE," Friday, Sept 9
SLAC National Accelerator Laboratory
ABSTRACT: The discovery of neutrino oscillations has opened an exciting avenue for physics searches beyond the Standard Model. In particular, a variety of experimental anomalies over the past twenty years can be jointly interpreted as evidence for a new fundamental particle called the sterile neutrino. The MicroBooNE experiment, a 170-ton liquid argon time projection chamber (LArTPC) currently operating in the Booster neutrino beam at Fermilab, will probe one of the sterile neutrino anomalies while also providing critical input for the development of future large-scale LArTPCs. After reviewing the status of neutrino physics, this talk will describe the MicroBooNE experiment and present a number of initial results. Future prospects will be discussed, including the integration of MicroBooNE into the Fermilab short baseline neutrino program.