1,460 research outputs found
Quantum Langevin model for exoergic ion-molecule reactions and inelastic processes
We presents a fully quantal version of the Langevin model for the total rate
of exoergic ion-molecule reactions or inelastic processes. The model, which is
derived from a rigorous multichannel quantum-defect formulation of bimolecular
processes, agrees with the classical Langevin model at sufficiently high
temperatures. It also gives the first analytic description of ion-molecule
reactions and inelastic processes in the ultracold regime where the quantum
nature of the relative motion between the reactants becomes important.Comment: 5 pages, 3 figure
Agrotechnologies towards Ecotechnologies the three pillars for developing Eco-design
International audienceTo boost agrotechnologies towards ecotechnologies ("environmental technologies" according to ETAP programme of EU, or "more ecologically productive technologies" in the context of agriculture), we need to strengthen a "triple bottom" system: -To take into account, in "Life Cycle Analysis" methodologies, the natural variability in time and space of these applications in land use. - To develop an overall approach for realistic machinery qualification, in order to feed the environmental burdens accurately through relevant data bases collected on agrotechnologies in real action. - To work on Eco-innovation processes, by deepening specific innovation tools and methods, for implementation of innovative solutions chosen according to LCA results. This paper presents the concept, develops the methods and illustrates them by examples of results on organic spreading technologies
Stationary Metrics and Optical Zermelo-Randers-Finsler Geometry
We consider a triality between the Zermelo navigation problem, the geodesic
flow on a Finslerian geometry of Randers type, and spacetimes in one dimension
higher admitting a timelike conformal Killing vector field. From the latter
viewpoint, the data of the Zermelo problem are encoded in a (conformally)
Painleve-Gullstrand form of the spacetime metric, whereas the data of the
Randers problem are encoded in a stationary generalisation of the usual optical
metric. We discuss how the spacetime viewpoint gives a simple and physical
perspective on various issues, including how Finsler geometries with constant
flag curvature always map to conformally flat spacetimes and that the Finsler
condition maps to either a causality condition or it breaks down at an
ergo-surface in the spacetime picture. The gauge equivalence in this network of
relations is considered as well as the connection to analogue models and the
viewpoint of magnetic flows. We provide a variety of examples.Comment: 37 pages, 6 figure
Charge Exchange and Chemical Reactions with Trapped Th
We have measured the reaction rates of trapped, buffer gas cooled Th
and various gases and have analyzed the reaction products using trapped ion
mass spectrometry techniques. Ion trap lifetimes are usually limited by
reactions with background molecules, and the high electron affinity of multiply
charged ions such as Th make them more prone to loss. Our results show
that reactions of Th with carbon dioxide, methane, and oxygen all occur
near the classical Langevin rate, while reaction rates with argon, hydrogen,
and nitrogen are orders of magnitude lower. Reactions of Th with oxygen
and methane proceed primarily via charge exchange, while simultaneous charge
exchange and chemical reaction occurs between Th and carbon dioxide.
Loss rates of Th in helium are consistent with reaction with impurities
in the gas. Reaction rates of Th with nitrogen and argon depend on the
internal electronic configuration of the Th.Comment: 9 pages, 10 figures, 4 tables. Submitted to PR
Evidence of a new state in Be observed in the Li -decay
Coincidences between charged particles emitted in the -decay of
Li were observed using highly segmented detectors. The breakup channels
involving three particles were studied in full kinematics allowing for the
reconstruction of the excitation energy of the Be states participating
in the decay. In particular, the contribution of a previously unobserved state
at 16.3 MeV in Be has been identified selecting the +
He + He+n channel. The angular correlations between the
particle and the center of mass of the He+n system favors spin and
parity assignment of 3/2 for this state as well as for the previously known
state at 18 MeV.Comment: 13 pages, 6 figure
Generalized dynamical density functional theory for classical fluids and the significance of inertia and hydrodynamic interactions
We study the dynamics of a colloidal fluid including inertia and hydrodynamic
interactions, two effects which strongly influence the non-equilibrium
properties of the system. We derive a general dynamical density functional
theory (DDFT) which shows very good agreement with full Langevin dynamics. In
suitable limits, we recover existing DDFTs and a Navier-Stokes-like equation
with additional non-local terms.Comment: 5 pages, 4 figures, 4 supplementary movie files, I supplementary pd
Ion Mobility Shift of Isotopologues in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at Elevated Effective Temperatures
Ion mobility spectrometers (IMS) separate ions mainly by ion–neutral collision cross section and to a lesser extent by ion mass and effective temperature. When investigating isotopologues, the difference in collision cross section can be assumed negligible. Since the mobility shift of isotopologues is thus mainly caused by their difference in mass and effective temperature, the investigation of isotopologues can provide important insights into the theory of ion mobility. However, in classical IMS operated at ambient pressure, cluster formation with neutral molecules occurs, which significantly influences the mobility shift of isotopologues and thus makes a sound investigation of the effect of ion mass and effective temperature on the ion mobility difficult. In this work, the relative ion mobility of several organic compounds and their 13C-labeled isotopologues is studied in a High Kinetic Energy Ion Mobility Spectrometer (HiKE-IMS) at high reduced electric fields up to 120 Td, which allows the investigation of nonclustered ion species and thus enables a sound investigation of the mobility shift of isotopologues. The results show that the measured relative ion mobilities of isotopologues having the same effective temperature and, thus, their ion mass dominating the relative ion mobility agree well with theoretical relative ion mobilities predicted by the theory of ion mobility
Time on a Rotating Platform
Traditional clock synchronisation on a rotating platform is shown to be
incompatible with the experimentally established transformation of time. The
latter transformation leads directly to solve this problem through noninvariant
one-way speed of light. The conventionality of some features of relativity
theory allows full compatibility with existing experimental evidence.Comment: 12 pages, Latex, no figure. Copies available at [email protected]
accepted for publication in Found. Phys. Let
Unification of dynamic density functional theory for colloidal fluids to include inertia and hydrodynamic interactions: derivation and numerical experiments.
Starting from the Kramers equation for the phase-space dynamics of the N-body probability distribution, we derive a dynamical density functional theory (DDFT) for colloidal fluids including the effects of inertia and hydrodynamic interactions (HI). We compare the resulting theory to extensive Langevin dynamics simulations for both hard rod systems and three-dimensional hard sphere systems with radially symmetric external potentials. As well as demonstrating the accuracy of the new DDFT, by comparing with previous DDFTs which neglect inertia, HI, or both, we also scrutinize the significance of including these effects. Close to local equilibrium we derive a continuum equation from the microscopic dynamics which is a generalized Navier–Stokes-like equation with additional non-local terms governing the effects of HI. For the overdamped limit we recover analogues of existing configuration-space DDFTs but with a novel diffusion tensor
Multiple light scattering in nematic liquid crystals
We present a rigorous treatment of the diffusion approximation for multiple
light scattering in anisotropic random media, and apply it to director
fluctuations in a nematic liquid crystal. For a typical nematic material, 5CB,
we give numerical values of the diffusion constants and .
We also calculate the temporal autocorrelation function measured in Diffusing
Wave Spectroscopy.Comment: 5 pages RevTeX, 1 postscript figure, to be published in Phys. Rev. E
(Rapid Communication
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