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Title: Moment theory of ion-neutral reactions in traps and similar devices

Abstract

Recent moment theories of ion motion in traps and similar devices are extended to mixtures of neutral gases in which one or more components can under go infrequent reaction with the ion of interest. Expressions are developed for the the position and time dependence of the ion-neutral reaction rate coefficient in such circumstances. These expressions are incorporated into the sets of coupled differential equations that govern the average ion velocity and kinetic and internal energies. This provides a consistent description of the ion transport and reaction coefficients.

Authors:
 [1];  [1];  [2]
  1. Chatham College, Pittsburgh
  2. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
931466
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A; Journal Volume: 111; Journal Issue: 15
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DIFFERENTIAL EQUATIONS; GASES; IONS; REACTION KINETICS; TRAPS; Gases; kinetic theory; electric field; time-dependent fields; position-dependent fields

Citation Formats

Viehland, Mr. Larry A., Danailov, Daniel M., and Goeringer, Doug. Moment theory of ion-neutral reactions in traps and similar devices. United States: N. p., 2007. Web. doi:10.1021/jp066096m.
Viehland, Mr. Larry A., Danailov, Daniel M., & Goeringer, Doug. Moment theory of ion-neutral reactions in traps and similar devices. United States. doi:10.1021/jp066096m.
Viehland, Mr. Larry A., Danailov, Daniel M., and Goeringer, Doug. Mon . "Moment theory of ion-neutral reactions in traps and similar devices". United States. doi:10.1021/jp066096m.
@article{osti_931466,
title = {Moment theory of ion-neutral reactions in traps and similar devices},
author = {Viehland, Mr. Larry A. and Danailov, Daniel M. and Goeringer, Doug},
abstractNote = {Recent moment theories of ion motion in traps and similar devices are extended to mixtures of neutral gases in which one or more components can under go infrequent reaction with the ion of interest. Expressions are developed for the the position and time dependence of the ion-neutral reaction rate coefficient in such circumstances. These expressions are incorporated into the sets of coupled differential equations that govern the average ion velocity and kinetic and internal energies. This provides a consistent description of the ion transport and reaction coefficients.},
doi = {10.1021/jp066096m},
journal = {Journal of Physical Chemistry A},
number = 15,
volume = 111,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The two-temperature moment theory of ion motion in devices where the external fields vary with position and time is applied to ideal quadrupole ion traps. In first approximation, the theory gives differential equations with collision frequencies that vary with the effective temperature characterizing the relative kinetic energy of the ion-neutral collisions. Solutions of the set of coupled differential equations provide the ion number density, average velocities, average energy and average temperature as functions of time and of position in the apparatus. That information also enables the effective temperature for the ion ensemble and the position-dependent energy density to be determinedmore » as a function of time. Solutions of the coupled equations are discussed for the Maxwell model, rigid spheres and general ion-neutral interactions.« less
  • This paper extends the momentum-transfer theory of drift tubes to ion traps and similar devices where the electric fields vary with both position and time. The collision frequencies that are incorporated into two-temperature and multi-temperature moment theories are given precise microscopic definitions instead of being treated as adjustable parameters.
  • This papers extends to molecules the moment theory of ion traps and similar devices where the electric elds vary with both position and time. It is based on the Wang Chang-Uhlenbeck-de Boer equation and a series of successive approximations based on the Maxwell model and the assumption that all other moments of the ion distribution function vary much less rapidly with position and time than does the ion number density. Two versions of the theory are presented: a simpler one, based on spherical-polar basis functions, and a more comprehensive one, based on Cartesian functions. Two-temperature and multi-temperature moment theories weremore » presented for atomic ion motion in traps and similar devices where there are external fields that vary with position and time. The relative advantages and disadvantages of the two theories were briefly discussed. The accuracy of the two-temperature moment theory was demonstrated in a second paper that considered Field-Asymmetric Ion Mobility Spectrometry. The two-temperature theory was then applied to ideal quadrupole ion traps. The purpose of this paper is to extend the theory to molecular ions and/or neutrals.« less
  • Recent moment theories of ion motion in devices where the external fields vary with position and time are applied to non-ideal ion traps. In first approximation, the theories give differential equations with collision frequencies that vary with the effective temperature characterizing the relative kinetic energy of the ion-neutral collisions. Solutions of the set of coupled differential equations provide the ion number density, average velocities, average energies, and average temperatures as functions of time and of position in the apparatus. Solutions of the coupled equations are discussed for the Maxwell model, rigid spheres, and general ion-neutral interactions. A surprising finding ismore » that ac fields on the end caps lead to changes in the stability region for ion motion in traps, changes that can cause ion injection both for small and large values of the ac field applied to the rings.« less
  • The kinetics of neutral atoms in a plasma undergoing charge-exchange, ionization, and recombination is considered. It is shown that if the mean-free path divided by the macroscopic scale length is constant, it is possible to introduce self-similar variables in the Boltzmann equation for the neutral particles. This equation is then solved analytically, and the nonlocal transport of heat and particles is calculated. Since the mean-free path increases with increasing energy, a one-sided, high-energy tail is formed in the neutral distribution function. This tail may contribute significantly to the heat and particle fluxes. When this is the case, the fluid approximationmore » of these quantities breaks down at arbitrarily short mean-free paths. {copyright} {ital 1996 American Institute of Physics.}« less