3,434 research outputs found
Three-body dynamics in single ionization of atomic hydrogen by 75 keV proton impact
Doubly differential cross sections (DDCS) for single ionization of atomic hydrogen by 75 keV proton impact have been measured as a function of the projectile scattering angle and energy loss. This pure three-body collision system represents a fundamental test case for the study of the reaction dynamics in few-body systems. A comparison between theory and experiment reveals that three-body dynamics is important at all scattering angles, and that an accurate description of the role of the projectile-target nucleus interaction as well as the second order projectile-electron interaction remains a major challenge to theory. However, progress is being made in understanding these higher order interactions and a better understanding of the collision dynamics seems possible --Abstract, page iii
An Analysis of Mature Consumers\u27 Reactions to Unsatisfactory Complaint Handling by Service Provider
In this nationwide survey, consumers over the age of 65 reported their reactions to a recalled unsatisfactory complaint experience that involved a service rendered. The study focused on the possible link between attributions of complainants for failure to obtain desired outcomes and subsequent behaviors. Inferences about causes and some demographic characteristics were found useful for explaining variation in anger reactions, negative word-of-mouth communications, repurchase behaviors, and estimations of the likelihood of future complaint actions among sampled seniors. Implications of results in terms of effective complaint handling by service organizations are discussed
Optical characterization of BiSe in a magnetic field: infrared evidence for magnetoelectric coupling in a topological insulator material
We present an infrared magneto-optical study of the highly thermoelectric
narrow-gap semiconductor BiSe. Far-infrared and mid-infrared (IR)
reflectance and transmission measurements have been performed in magnetic
fields oriented both parallel and perpendicular to the trigonal axis of
this layered material, and supplemented with UV-visible ellipsometry to obtain
the optical conductivity . With lowering of temperature we
observe narrowing of the Drude conductivity due to reduced quasiparticle
scattering, as well as the increase in the absorption edge due to direct
electronic transitions. Magnetic fields dramatically
renormalize and asymmetrically broaden the strongest far-IR optical phonon,
indicating interaction of the phonon with the continuum free-carrier spectrum
and significant magnetoelectric coupling. For the perpendicular field
orientation, electronic absorption is enhanced, and the plasma edge is slightly
shifted to higher energies. In both cases the direct transition energy is
softened in magnetic field.Comment: Final versio
Phosphorus forms and concentrations in soils under different land use in southwestern Saskatchewan
Non-Peer ReviewedPhosphorus (P) is an essential nutrient for all organisms. Insufficient or poorly available P can limit crop growth, requiring P fertilization. However, excess P can move from land to water, impairing water quality. Balancing P fertilization to maximize crop growth while limiting P loss requires a detailed knowledge of P forms and cycling. Different land use practices are expected to alter P cycling through differences in microbial populations, P inputs from vegetation and fertilizer, and management practices that affect soil chemical and physical properties. Understanding P cycling under different land uses can help to improve P use efficiency in agriculture. Presented here are the preliminary results of a research project investigating P forms and cycling in soils under different land uses in southwestern Saskatchewan
Scattering-Angle Dependence of Doubly Differential Cross Sections for Fragmentation of H₂ by Proton Impact
We have measured double differential cross sections (DDCS) for proton fragment formation for fixed projectile energy losses as a function of projectile scattering angle in 75 keV p + H2 collisions. An oscillating pattern was observed in the angular dependence of the DDCS with a frequency about twice as large as what we found earlier for nondissociative ionization. Possible origins for this frequency doubling are discussed
Two-Stage Rotational Disordering of a Molecular Crystal Surface: C\u3csub\u3e60\u3c/sub\u3e
We propose a two-stage mechanism for the rotational surface disordering phase transition of a molecular crystal, as realized in C60 fullerite. Our study, based on Monte Carlo simulations, uncovers the existence of a new intermediate regime, between a low-temperature ordered (2×2) state, and a high-temperature (1×1) disordered phase. In the intermediate regime there is partial disorder, strongest for a subset of particularly frustrated surface molecules. These concepts and calculations provide a coherent understanding of experimental observations, with possible extension to other molecular crystal surfaces
Fabrication and Characterization of Topological Insulator BiSe Nanocrystals
In the recently discovered class of materials known as topological
insulators, the presence of strong spin-orbit coupling causes certain
topological invariants in the bulk to differ from their values in vacuum. The
sudden change of invariants at the interface results in metallic, time reversal
invariant surface states whose properties are useful for applications in
spintronics and quantum computation. However, a key challenge is to fabricate
these materials on the nanoscale appropriate for devices and probing the
surface. To this end we have produced 2 nm thick nanocrystals of the
topological insulator BiSe via mechanical exfoliation. For crystals
thinner than 10 nm we observe the emergence of an additional mode in the Raman
spectrum. The emergent mode intensity together with the other results presented
here provide a recipe for production and thickness characterization of
BiSe nanocrystals.Comment: 4 pages, 3 figures (accepted for publication in Applied Physics
Letters
Probing TeV-scale gauge unification by hadronic collisions
Grand unified theories (GUTs) and extra dimensions are potential ingredients
of the new physics that may resolve various outstanding problems of the
Standard Model. If the inverse size of (one of) the extra dimension(s) is
smaller than the GUT scale and standard gauge bosons are allowed to propagate
in the bulk then, among other consequences, the evolution of the gauge
couplings deviates from the usual logarithmic running somewhat below and
between these two scales.
In this work, we show that if the compactification scale is the order of 10
TeV, then this modified running may be observable at the CERN Large Hadron
Collider in the dijet invariant mass distribution. We also demonstrate that
dijets are highly sensitive to the renormalization effects of the extra
dimensions, and are potential tools for determining the number of dimensions
and the value of the compactification scale.Comment: 10 pages, 2 figures, using JHEP styl
Collective Autoionization in Multiply-Excited Systems: A novel ionization process observed in Helium Nanodroplets
Free electron lasers (FELs) offer the unprecedented capability to study
reaction dynamics and image the structure of complex systems. When multiple
photons are absorbed in complex systems, a plasma-like state is formed where
many atoms are ionized on a femtosecond timescale. If multiphoton absorption is
resonantly-enhanced, the system becomes electronically-excited prior to plasma
formation, with subsequent decay paths which have been scarcely investigated to
date. Here, we show using helium nanodroplets as an example that these systems
can decay by a new type of process, named collective autoionization. In
addition, we show that this process is surprisingly efficient, leading to ion
abundances much greater than that of direct single-photon ionization. This
novel collective ionization process is expected to be important in many other
complex systems, e.g. macromolecules and nanoparticles, exposed to high
intensity radiation fields
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