Ion charge state

Figure 14. Double differential cross sections (ddcs — 2n dv v J for electron emission due to single, double, or triple ionization of Ar by 3.6-MeV/amu Au53+ ions. The DDCS for the specified recoil-ion charge states are added according to their relative contribution to the total cross section. CDW-EIS results (solid lines [73]) are shown along with the experimental data from Moshammer et at. [53], The experimental data are divided by 1.4. Cross sections at different ve are multiplied by factors of 10, respectively.

Fig. 7.2. Calculated [40] relative ion population as a function of ion charge state in solid Ti heated at temperatures ranging from 10 to lOOeV. Also shown in the same plot is the separation energy of the 2p-ls transitions as a function of the ion charge. Higher ionization stages from B-like Ti to O-like Ti are expected to emit in the range between 4,550 and 4,750 eV...

Herron, W.J. Goeringer, D.E. McLuckey, S.A. Product Ion Charge State Determination Via lon/lon Proton Transfer Reactions. Anal. Chem. 1996, 68, 257-262. 

Isotope peaks observed for proteins are mainly produced by the 12C and 13C mass difference of 1 mass unit. Once one molecular ion charge state is determined, the other charge states are readily assigned by spectral observation. ESI, MALDI, and FAB are usually used in the positive-ion mode, especially for protein MW determination therefore the proton mass must be used to calculate the ion mass, as shown in Table 15.7. 

Fig. 2. Stopping powers for He moving in Al (LT, linear theory). The total stopping power is separated into the ion charge states contribution and the capture and loss contribution.

Using this local orbital DF approach, we define the different ion charge states by the orbital occupancy, (for example, for He we take = ) Moreover, to be consistent, at the same time we have to take zero the hopping parameters between the atomic orbitals and the metal [19]. With these assumptions, we have to solve Hamiltonian (5) and calculate, say, [He ] and [He ]. 

We focus here into the radiative processes that modify the ion charge state, i.e., those that involve the capture of an electron from the target valence band. We do not include radiative relaxation processes in which one electron decays between two bound states of the ion, although they can be of the same importance in the description of a realistic neutralization and relaxation... 

In fact, this is not the only place that quantum mechanics enters the problem. The charge state of the projectile, which is a dynamic quantity varying over the allowed ion charge states as a function of velocity, as the projectile traverses the target, is also quantum mechanically determined. Although most treatments... 

Hence the resolving power of conventional IMS depends only on the drift voltage, gas temperature, and ion charge state, but no other ion property such as mobility or... 

This approach provides accurate D, and reproduces trends as a function of both temperature and ion charge state, and hence is the most sophisticated method currently known for calculation of mobilities for polyatomic ions with more than a few atoms. 

Equations 4.34 and 4.35 contain q, and the metrics of field-driven FAIMS depend on the ion charge state z in the same way as those for flow-driven systems (4.2.3). Hence the field drive greatly reduces the discrimination by mobility within same z, but not between ions of different z-... 

He, M. Reid, G.E. Shang, H. Lee, G.U. McLuckey, S.A. Dissociation of multiple protein ion charge states following a single gas-phase purification and concentration procedure. Anal. Chem. 2002, 74, 4653-4661. 

Figure 9.5 Isotopic distributions of intact Ub ions (charge state +10) before (a) and after (b, c, and d) precursor ion isolation (under exchange-out conditions). Panel (a) shows the extent of H retention on partially exchanged Ub (Ub ) by overlaying its spectrum with spectra of unlabeled (Ub), completely exchanged Ub (endpoint) and fully deuterated (Ub ) protein ions on a zoom-out scale. Panel (b) shows broadband isolation of Ub ions, and panels (c) and (d) illustrate Isolation of Ub ions representing con-formers C-l and C-2, respectively (the isolation windows are shown In panel (a)). Reproduced with permission from [25]...

ESI mass spectrum acquired under denaturing conditions (black trace in Figure 10.4) was noticeably higher. This suggests that the solvent accessible surface area of noncompact conformers of NEM-IFN, whose presence under near-native conditions is revealed by the protein ion charge state distribution analysis, is lower compared to the fully denatured species of IFN [3233]. However, this technique yields only a global measure of conformational disorder and, therefore, cannot provide any information that would allow these unfolding events to be localized within the protein structure. 

Fig. 9.40. Effect of precursor ion charge state on ETD product ion spectra of (a) the triply protonated peptide ion [KAAAKAAAK+H] and (b) the doubly protonated ion of the same peptide which only produces half of the possible c- and z-type fragments. Reproduced from Ref. [162] with permission. American Chemical Society, 2007.

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