Ionic cross section determination

The cross-sections for the reactions of primary and secondary ionic species with the gas in the source chamber of the spectrometer were determined by the beam model (38). Reactions of primary ions with gas molecules as the ions move under the action of the electric field from the plane of formation toward the ion exit slit will attenuate the beam in exponential fashion, so that the intensity Ip at the exit slit will be ... 

Charge exchange is important all along the high-LET tracks. The effective ionic charge is determined by cross sections of electron capture and loss, which depend predominantly on the ionic velocity. Electron loss may be simply described by an ionization of the incident ion in its own reference frame due to the impact of medium electrons and nuclei. Following Bohr (1948), Mozumder et al. (1968) wrote the cross section for this process as1... 

Up to this point we have considered only the conditions for resonances in the cross sections of small spherical particles of various kinds we have said nothing quantitative about their strengths and the frequencies at which they might occur other than brief introductory remarks about ionic crystals in the infrared and metals in the ultraviolet. To determine if a resonance is realizable, where it occurs, and its strength, we need to know how the dielectric function varies with frequency. Therefore, in the following sections we shall examine some of the preceding resonance conditions in the light of simple, but realistic, dielectric functions. 

Assume that the fractional abundance of an excited ionic state produced by electron impact on a given molecule under specified reaction conditions is known and that an ion-neutral reaction is known to occur preferentially with that ionic state. Then, by determining the cross section a for that reaction, with the reactant ion produced from a series of different molecules, and comparing these with a for the reaction using ions generated from the source molecule that yields the known fractional abundance of... 

Investigations on the doubly excited states of two electron systems under weakly coupled plasma have been performed by several authors. Such states usually occur as resonance states in electron atom collisions and are usually autoionizing [225]. Many of these states appear in solar flare and corona [226,227] and contribute significantly to the excitation cross-sections required to determine the rate coefficients for transitions between ionic states in a high temperature plasma. These are particularly important for dielectronic recombination processes which occur in low density high temperature plasma, occurring e.g. in solar corona. Coronal equilibrium is usually guided by the balance between the rates of different ionization and... 

We have recently developed a gas-phase ion chromatography technique and applied it to carbon cluster cations " " and anions""". A pulse of mass-selected cluster ions is injected into a high-pressure drift cell filled with 2-5 torr of helium. The ionic mobilities of different isomeric structures depend on their different collision cross-sections with He, and the isomers are therefore separated while drifting through the cell, under the influence of a weak electric field. The absolute value of the ionic mobility for a given cluster together with computer simulations often allows unambiguous determination of the cluster... 

In order to determine the effect of the ionic charges on the cross-sectional dimensions, i.e. on the extension of the side chains, X-ray scattering experiments were performed. In the high q -regime the form factor of a rod-like structure decays as ... 

Basically, one distinguishes between pair creation, where the electron and positron are produced in free (continuum) states and pair creation with an electron in a bound state of one of the ions, for example, in a K-shell state. The latter process is also called bound-free pair production. Pair creation with electron capture into a bound state of the ion changes the charge state of the ion represents one of the major loss processes affecting the stability of ion beams in relativistic heavy-ion colliders. The corresponding cross-section for electron capture is of the order of 100 bam for RHIC energies in U92+(100 GeV/u) -I- U92+(100 GeV/u) collisions and determines the lifetime of ionic charge states in the beam and then the luminosity. 

Transference numbers are determined by the details of ionic conduction, which are understood mainly through measurements of either the resistance to current flow in solution or its reciprocal, the conductance, L (31, 32). The value of L for a segment of solution immersed in an electric field is directly proportional to the cross-sectional area perpendicular to the field vector and is inversely proportional to the length of the segment along the field. The proportionality constant is the conductivity, k, which is an intrinsic property of the solution ... 

Using the fractional abundances obtained from the analysis of the above data and the data obtained using their previous method [221], they were able to determine the cross-sections for the separate ionic states for both reactions (127) and (133). The cross-sections for reaction (127) with only 0 ( S) ions and for reaction (133) with only 0 CD) ions are shown in Fig. 25 (curves denoted by RV), together with the results of other authors which are not necessarily for a single electronic state. It was concluded from their results that the contribution of the state to reaction (127) is negligible, at least in the eV region. An indication that this is true has also been reported by Stebbings et al. [227]. 

Process (22a) requires a crossing between the ionic curve of the NO -Q pair and the covalent (largely repulsive) curve due to NO-Q interaction. This crossing is followed by rapid charge recombination. Quenching cross-sections may be determined from the distance R at which the crossing takes place. Similarity to alkaline atoms is suggested by Fig. 2, in which the ionization potentials of Na, K, and NO are taken as a common reference potential. Effective ionization potentials of the A, C, and D states of NO are seen to be close to those of the Na(3P) and K(4F) states. 

This observed pattern of charge transfer and switching processes is consistent with the vertical-transition model (Franck-Condon principle) as discussed by Bearman et al. (1976), who interpreted the cross sections for ionic excitation in low-energy charge-transfer collision between HeJ and some diatomic neutrals. In analogy to that, in the cases of KrJ reactions, it is not the total recombination energy RE(KrJ) = 12.85 eV that is available, but only the effective recombination energy Reeff(KrJ) = 11.91 eV, which is determined, as shown in Fig. 6, by the vertical transition from KrJ to the repulsive state of JCr-Kr at the equilibrium distance f o(Kr2 ) ... 

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