STM studies of island nucleation during hyperthermal atom deposition

2002 ◽  
Vol 749 ◽  
Author(s):  
Joshua M. Pomeroy ◽  
Joel D. Brock
Keyword(s):  
Kinetic Energy ◽  
Ion Beam ◽  
Mean Field ◽  
Scaling Exponent ◽  
Island Nucleation ◽  
Precise Control ◽  
Ion Kinetic Energy ◽  
The Mean ◽  
Sputter Erosion ◽  
Hyperthermal Energy

ABSTRACTWe report fundamental changes in island nucleation dynamics as the kinetic energy of the constituent particles used for film grown is increased. A hyperthermal energy ion beam-line with precise control over ion kinetic energy was used to grow copper islands on a Cu(100) substrate. Dramatic increases in island densities were observed with increasing kinetic energy from thermal energies to 150 eV. We find that sputter erosion and the formation of adatom-vacancy pairs contribute to this increase. In addition, variations in flux and temperature suggest that the mean-field scaling exponent is sensitive to atomistic mechanisms activated by the ion beam.

KINETIC ENERGY AND PHASE SEPARATION IN A DOPED ANTIFERROMAGNET

1995 ◽  
Vol 09 (24) ◽  
pp. 1623-1629 ◽  
Author(s):  
XIN XU ◽  
YUN SONG ◽  
SHIPING FENG
Keyword(s):  
Phase Separation ◽  
Kinetic Energy ◽  
Ground State ◽  
Mean Field ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Numerical Result ◽  
The Mean ◽  
State Kinetic

The ground-state kinetic energy of the t-J model is studied within the mean field approximation by using the fermion-spin transformation, the results show that the mean field ground-state kinetic energy is close to the numerical result at under dopings, and roughly consistent with the numerical result at optimal dopings. It is also shown that the frustration term J′ is favourable to diminish the range of the phase seperation in the t-J model.

scholarly journals Percolation–like scaling exponents for minimal paths and trees in the stochastic mean field model

2005 ◽  
Vol 461 (2055) ◽  
pp. 825-838 ◽  
Author(s):  
David J. Aldous
Keyword(s):  
Minimum Spanning Tree ◽  
Optimization Problems ◽  
Travelling Salesman Problem ◽  
Mean Field ◽  
Independent Random Variables ◽  
Cavity Method ◽  
Scaling Exponent ◽  
Scaling Exponents ◽  
Mean Field Model ◽  
The Mean

In the mean field (or random link) model there are n points and inter-point distances are independent random variables. For 0 < ℓ < ∞ and in the n → ∞ limit, let δ ( ℓ ) = 1/ n times the maximum number of steps in a path whose average step-length is ≤ ℓ . The function δ ( ℓ ) is analogous to the percolation function in percolation theory: there is a critical value ℓ * = e −1 at which δ (·) becomes non-zero, and (presumably) a scaling exponent β in the sense δ ( ℓ ) ≈ ( ℓ − ℓ * ) β . Recently developed probabilistic methodology (in some sense a rephrasing of the cavity method developed in the 1980s by Mézard and Parisi) provides a simple, albeit non-rigorous, way of writing down such functions in terms of solutions of fixed-point equations for probability distributions. Solving numerically gives convincing evidence that β = 3. A parallel study with trees and connected edge-sets in place of paths gives scaling exponent 2, while the analogue for classical percolation has scaling exponent 1. The new exponents coincide with those recently found in a different context (comparing optimal and near-optimal solutions of the mean-field travelling salesman problem (TSP) and the minimum spanning tree (MST) problem), and reinforce the suggestion that scaling exponents determine universality classes for optimization problems on random points.

Ejected Product Energy Distributions from Laser Ablated Solids

1988 ◽  
Vol 129 ◽  
Author(s):  
H. Helvajian ◽  
R. P. Welle
Keyword(s):  
Laser Ablation ◽  
Kinetic Energy ◽  
Product Formation ◽  
Uv Laser ◽  
Energy Distributions ◽  
Laser Threshold ◽  
Ion Kinetic Energy ◽  
The Mean ◽  
Mean Kinetic Energy ◽  
Kinetic Energy Distributions

ABSTRACTAt laser threshold fluences near ion product formation, we have measured the ejected ion kinetic-energy distributions from the UV laser ablation of crystalline aluminum and silver targets. The mean kinetic energy is found to be hyperthermal.

scholarly journals On nonlinear Alfvén-cyclotron waves in multi-species plasma

2010 ◽  
Vol 77 (3) ◽  
pp. 385-403 ◽  
Author(s):  
ECKART MARSCH ◽  
DANIEL VERSCHAREN
Keyword(s):  
Magnetic Field ◽  
Kinetic Energy ◽  
Electric Field ◽  
Transverse Magnetic Field ◽  
Acoustic Waves ◽  
Mean Field ◽  
Transverse Magnetic ◽  
Longitudinal Electric Field ◽  
Mhd Turbulence ◽  
The Mean

AbstractLarge-amplitude Alfvén waves are ubiquitous in space plasmas and a main component of magnetohydrodynamic (MHD) turbulence in the heliosphere. As pump waves, they are prone to parametric instability by which they can generate cyclotron and acoustic daughter waves. Here, we revisit a related process within the framework of the multi-fluid equations for a plasma consisting of many species. The nonlinear coupling of the Alfvén wave to acoustic waves is studied, and a set of compressive and coupled-wave equations for the transverse magnetic field and longitudinal electric field is derived for waves propagating along the mean-field direction. It turns out that slightly compressive Alfvén waves exert, through induced gyro-radius and kinetic-energy modulations, an electromotive force on the particles in association with a longitudinal electric field, which has a potential that is given by the gradient of the transverse kinetic energy of the particles gyrating about the mean field. This in turn drives electric fluctuations (sound and ion-acoustic waves) along the mean magnetic field, which can nonlinearly react back on the transverse magnetic field. Mutually coupled Alfvén-cyclotron--acoustic waves are thus excited, a nonlinear process that can drive a cascade of wave energy in the plasma, and may generate compressive microturbulence. These driven electric fluctuations might have consequences for the dissipation of an MHD turbulence and, thus, for the heating and acceleration of particles in the solar wind.

Classical Kinetic Theory

2018 ◽  
Author(s):  
Klaus Morawetz
Keyword(s):  
Kinetic Equation ◽  
Equation Of State ◽  
Mean Field ◽  
Ideal Gas ◽  
Hydrodynamic Equations ◽  
Free Particles ◽  
Internal Mechanism ◽  
The Mean ◽  
Energy Gains ◽  
Non Locality

The classical non-ideal gas shows that the two original concepts of the pressure based of the motion and the forces have eventually developed into drift and dissipation contributions. Collisions of realistic particles are nonlocal and non-instant. A collision delay characterizes the effective duration of collisions, and three displacements, describe its effective non-locality. Consequently, the scattering integral of kinetic equation is nonlocal and non-instant. The non-instant and nonlocal corrections to the scattering integral directly result in the virial corrections to the equation of state. The interaction of particles via long-range potential tails is approximated by a mean field which acts as an external field. The effect of the mean field on free particles is covered by the momentum drift. The effect of the mean field on the colliding pairs causes the momentum and the energy gains which enter the scattering integral and lead to an internal mechanism of energy conversion. The entropy production is shown and the nonequilibrium hydrodynamic equations are derived. Two concepts of quasiparticle, the spectral and the variational one, are explored with the help of the virial of forces.

scholarly journals Evidence of exactness of the mean-field theory in the nonextensive regime of long-range classical spin models

2000 ◽  
Vol 61 (17) ◽  
pp. 11521-11528 ◽  
Author(s):  
Sergio A. Cannas ◽  
A. C. N. de Magalhães ◽  
Francisco A. Tamarit
Keyword(s):  
Field Theory ◽  
Long Range ◽  
Mean Field Theory ◽  
Mean Field ◽  
Spin Models ◽  
Classical Spin ◽  
The Mean ◽  
Classical Spin Models

scholarly journals The Mean-field Behavior of Processor Sharing Systems with General Job Lengths Under the SQ(d) Policy

2019 ◽  
Vol 46 (3) ◽  
pp. 54-55
Author(s):  
Thirupathaiah Vasantam ◽  
Arpan Mukhopadhyay ◽  
Ravi R. Mazumdar
Keyword(s):  
Mean Field ◽  
Processor Sharing ◽  
Field Behavior ◽  
The Mean
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