120 research outputs found
Linewidths in bound state resonances for helium scattering from Si(111)-(1x1)H
Helium-3 spin-echo measurements of resonant scattering from the Si(111)â(1 Ă 1)H surface, in the energy range 4â14 meV, are presented. The measurements have high energy resolution yet they reveal bound state resonance features with uniformly broad linewidths. We show that exact quantum mechanical calculations of the elastic scattering, using the existing potential for the helium/Si(111)â(1 Ă 1)H interaction, cannot reproduce the linewidths seen in the experiment. Further calculations rule out inelastic and other mechanisms that might give rise to losses from the elastic scattering channels. We show that corrugation in the attractive part of the atomâsurface potential is the most likely origin of the experimental lineshapes
State-Insensitive Trapping of Alkaline-Earth Atoms in a Nanofiber-Based Optical Dipole Trap
Neutral atoms trapped in the evanescent optical potentials of nanotapered
optical fibers are a promising platform for developing quantum technologies and
exploring fundamental science, such as quantum networks and quantum
electrodynamics. Building on the successful advancements with trapped alkali
atoms, here we demonstrate a state-insensitive optical dipole trap for
strontium-88, an alkaline-earth atom, using the evanescent fields of a
nanotapered optical fiber. Leveraging the low laser-cooling temperatures of
K readily achievable with strontium, we demonstrate trapping in
record low trap depths corresponding to K. Further, employing a
double magic wavelength trapping scheme, we realize state-insensitive trapping
on the kilohertz-wide 5s^{2}\;^{1}\!S_{0}-5s5p\;^{3}\!P_{1,|m|=1} cooling
transition, which we verify by performing near-surface high-resolution
spectroscopy of the atomic transition. This allows us to experimentally find
and verify the state insensitivity of the trap nearby a theoretically predicted
magic wavelength of 435.827(25) nm. Given the non-magnetic ground state and low
collisional scattering length of strontium-88, this work also lays the
foundation for developing versatile and robust matter-wave atomtronic circuits
over nanophotonic waveguides.Comment: 14 pages, 15 figure
A new class of semiclassical wave function uniformizations
We present a new semiclassical technique which relies on replacing
complicated classical manifold structure with simpler manifolds, which are then
evaluated by the usual semiclassical rules. Under circumstances where the
original manifold structure gives poor or useless results semiclassically the
replacement manifolds can yield remarkable accuracy. We give several working
examples to illustrate the theory presented here.Comment: 12 pages (incl. 12 figures
Emergence of four dimensional quantum mechanics from a deterministic theory in 11 dimensions
We develop a deterministic theory which accounts for the coupling of a high dimensional continuum of environmental excitations (called gravonons) to massive particle in a very localized and very weak fashion. For the model presented Schrodinger's equation can be solved practically exactly in 11 spacetime dimensions and the result demonstrates that as a function of time an incoming matter wave incident on a screen extinguishes, except at a single interaction center on the detection screen. This transition is reminiscent of the wave - particle duality arising from the "collapse" (also called "process one") postulated in the Copenhagen-von Neumann interpretation. In our theory it is replaced by a sticking process of the particle from the vacuum to the surface of the detection screen. This situation was verified in experiments by using massive molecules. In our theory this "wave-particle transition" is connected to the different dimensionalities of the space for particle motion and the gravonon dynamics, the latter propagating in the hidden dimensions of 11 dimensional spacetime. The fact that the particle is detected at apparently statistically determined points on the screen is traced back to the weakness and locality of the interaction with the gravonons which allows coupling on the energy shell alone. Although the theory exhibits a completely deterministic "chooser" mechanism for single site sticking, an apparent statistical character results, as it is found in the experiments, due to small heterogeneities in the atomic and gravonon structures
Global Potentials for the Interaction between Rare Gases and Graphene-Based Surfaces: An AtomâBond Pairwise Additive Representation
Raman spectroscopy as a tool to determine the thermal maturity of organic matter : application to sedimentary, metamorphic and structural geology
Raman spectrometry is a rapid, non-destructive alternative to conventional tools employed to assess the thermal alteration of organic matter (OM). Raman may be used to determine vitrinite reflectance equivalent OM maturity values for petroleum exploration, to provide temperature data for metamorphic studies, and to determine the maximum temperatures reached in fault zones. To achieve the wider utilisation of Raman, the spectrum processing method, and the positions and nomenclature of Raman bands and parameters, all need to be standardized. We assess the most widely used Raman parameters as well as the best analytical practices that have been proposed. Raman band separation and G-band full-width at half-maximum are the best parameters to estimate the maturity for rocks following diagenesisâmetagenesis. For metamorphic studies, the ratios of band areas after performing deconvolution are generally used. Further work is needed on the second-order region, as well as assessing the potential of using integrated areas on the whole spectrum, to increase the calibrated temperature range of Raman parameters. Applying Raman spectroscopy on faults has potential to be able to infer both temperature and deformation processes. We propose a unified terminology for OM Raman bands and parameters that should be adopted in the future. The popular method of fitting several functions to a spectrum is generally unnecessary, as Raman parameters determined from an un-deconvoluted spectrum can track the maturity of OM. To progress the Raman application as a geothermometer a standardized approach must be developed and tested by means of an interlaboratory calibration exercise using reference materials
Dolomitic marbles from the ultrahigh-pressure metamorphic Kimi complex in Rhodope, N.E. Greece
Koexistierende Cummingtonite und Hornblenden in Amphiboliten des Schneeberger Zuges, Tirol, ïżœsterreich
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