Electron capture cross-section

Negative Cl can give excellent results for certain types of compounds. Compounds with electronegative substituents and unsaturation can be expected to have a large electron capture cross-section and thus work well in the negative ion mode. Frequently, much higher sensitivity is obtained for these compound types in the negative ion mode than under positive ion conditions. In addition, the molecular ion is usually very abundant. The... 

Table 4. Single-electron capture cross-sections on the n = 3 levels (in 10 cm ). (For comparison with Dijkkamp results, the collision energy is given in parenthesis...

Table 5. Values of the single-electron capture cross-sections for the and states (in 10" cm ).

The results summarized here illustrate the important role surface states play in C>2 evolution from photoexcited TiC>2 and provide an example of a quantitative determination of the density and electron capture cross section of these states. 

P. Barragan, A.-T. Le, C.D. Lin, Hyperspherical dose-coupling calculations for electron-capture cross sections in low-energy Ne10+ + H(ls) collisions, Phys. Rev. A 74 (2006) 012720. 

The recombination rate constant k°ec(U = UFB) can be expressed as the product of the doping density Nd, the thermal velocity v of electrons and the electron capture cross section tr of X+ ... 

We note that for the molecular case, our results give a good description of the electron capture and electron loss for the collision. For > H2 our results are proportionally lower that those reported by Gealy et al. [36] which were normalized to 6.95 X 10 cm at = 2.0 keV. If we use the same normalization, our results agree well with the experiment. We also note that for the molecular case, the lower the energy of the projectile, the smaller the electron capture cross section, contrary to the atomic case where there is resonant electron transfer. This is a molecular effect, since the closed shell of molecular hydrogen is more stable than the open shell in the atomic case, and thus the electron capture cross section for H2 is not one half that for... 

Removal of some of the internal energy of the XY " ion on collision with a neutral molecule has been invoked to explain the pressure dependence of the electron capture cross sections of 02 (13), NO (22), and N20 (68) in the gas phase. 

The previous examples were for direct scattering processes, i.e., for the channel where the projectile does not alter its charge. In the next section, we will discuss the electron capture cross section. 

The term %J R)=hlTJ, R) represents the autodetachment lifetime of the anion before the loss of the electron. The parameter o p(E) is defined as the electron capture cross section, which is approximated by... 

Careful selection of the derivatization technique may also be employed to enhance the detection limit of an analyte. The conversion of amphetamines to tetrafluorophthaloyl derivatives yields compounds possessing high electron capture cross-sections and the sensitivity toward such compounds, using negative ion chemical ionization (NICI) can be better than that achieved using positive ion formation by two orders of magnitude. Employing NICI in conjunction with SIM, the detection of amphetamine derivatives in quantities as small as 10 fg (SOamol) may be effected. 

Fig. 4.1. CDW-EIS cakulatioas of a for protons and antiprolons on helium by Fainstein et al. [4.5 are shown as soUd curves. The dashed curve shows the single electron capture cross section for p on helium as measured by Rudd et al. [4.41] and Shah and Gilbody [4.19]. The hatched area above the energy axis indicates velocities around that of the target elections.

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