40 research outputs found
Angular Distribution of Auger Electrons Emitted through the Resonant Transfer and Excitation Process Following O⁵⁺+He Collisions
This Letter reports the first measurements of the angular distribution of Auger electrons emitted from the decay of the (1s2s2p2)3D O4+** doubly excited state formed predominantly through resonant transfer and excitation (RTE) in collisions of 13-MeV O5+ projectiles with He. The (1s2s2p2)3D angular distribution is strongly peaked along the beam direction, in agreement with recent calculations of the RTE angle-dependent impulse approximation. Furthermore, interference effects between the RTE and the elastic target direct-ionization channels are observed
Double Excitation of He by Fast Ions
Autoionization of He atoms following double excitation by electrons, protons, CQ+ (Q=4-6), and FQ+ (Q=7-9) ions has been studied. The electron-emission yields from the doubly excited 2s2(1S), 2s2p(1P), and 2p2(1P) states were measured at the reduced projectile energy of 1.5 MeV/nucleon for observation angles between 10°and 60°. The results indicate excitation to the 2s2(1S) and 2p2(1D) states increases as approximately Q3, while excitation to the 2s2p(1P) state varies as approximately Q2, where Q is the charge of the projectile. These charge dependences are significantly less than the Q4 dependence expected in the independent-electron model, suggesting the interaction between the two target electrons is important in creating the doubly excited states
A Monte Carlo simulation of ion transport at finite temperatures
We have developed a Monte Carlo simulation for ion transport in hot
background gases, which is an alternative way of solving the corresponding
Boltzmann equation that determines the distribution function of ions. We
consider the limit of low ion densities when the distribution function of the
background gas remains unchanged due to collision with ions. A special
attention has been paid to properly treat the thermal motion of the host gas
particles and their influence on ions, which is very important at low electric
fields, when the mean ion energy is comparable to the thermal energy of the
host gas. We found the conditional probability distribution of gas velocities
that correspond to an ion of specific velocity which collides with a gas
particle. Also, we have derived exact analytical formulas for piecewise
calculation of the collision frequency integrals. We address the cases when the
background gas is monocomponent and when it is a mixture of different gases.
The developed techniques described here are required for Monte Carlo
simulations of ion transport and for hybrid models of non-equilibrium plasmas.
The range of energies where it is necessary to apply the technique has been
defined. The results we obtained are in excellent agreement with the existing
ones obtained by complementary methods. Having verified our algorithm, we were
able to produce calculations for Ar ions in Ar and propose them as a new
benchmark for thermal effects. The developed method is widely applicable for
solving the Boltzmann equation that appears in many different contexts in
physics.Comment: 14 page
The effect of the regularity of the error process on the performance of kernel regression estimators
This article considers estimation of regression function ff in the fixed design model Y(xi)=f(xi)+ϵ(xi),i=1, ¦,nY(xi)=f(xi)+ϵ(xi),i=1, ¦,n , by use of the Gasser and Müller kernel estimator. The point set {xi}ni=1⊂[0,1]{xi}i=1n⊂[0,1] constitutes the sampling design points, and ϵ(xi)ϵ(xi) are correlated errors. The error process ϵϵ is assumed to satisfy certain regularity conditions, namely, it has exactly kk ( =0,1,2, ¦=0,1,2, ¦ ) quadratic mean derivatives (q.m.d.). The quality of the estimation is measured by the mean squared error (MSE). Here the asymptotic results of the mean squared error are established. We found that the optimal bandwidth depends on the (2k+1)(2k+1) th mixed partial derivatives of the autocovariance function along the diagonal of the unit square. Simulation results for the model of kk th order integrated Brownian motion error are given in order to assess the effect of the regularity of this error process on the performance of the kernel estimator