Triple ionization

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.

O triple Ionization by R A Single ionization by He A Doubie ionization by He A Triple ionization by He ... 

Figure 23 Cross sections for single, double, and triple ionization of neon by singly charged hydrogen and helium ions. (From Refs. 17 and 78.)...

Triple ionization of the heavier noble gases has been reported by Kruse et al. (1991) and Helms et al. (1994, 1995a), and again the influence of inner shell effects is notable and quickly becomes the dominant mechanism for this process. 

The Fano-ADC technique outlined above can be generalized to the case of multiply ionized systems. Full description of the effect of the additional vacancies requires, of course, an ab initio approach that explicitly takes into account multiple ionization. In the case of a single additional charge, the ADC scheme for doubly ionized states would be appropriate. Such a scheme was developed by Schirmer and Barth [31]. The extended second-order ADC technique for double ionization [31] treats explicitly the two-hole (2h) and the three-hole one-particle (3hlp) excitation classes up to the second and first orders, respectively. Fano-ADC(2)x for decay widths of doubly ionized states embedded into triple ionization continua has been developed in Ref. [32]. 

On the methodology side, it would be important to generalize the Fano-ADC theory of Section 2 to the case of triple ionization using the second-order ADC scheme of Ref. [80]. Moreover, the problem of different level of treatment of adjacent excitation classes within the existing ADC... 

Figure Bl.10.11. Electron impact double ionization triple coincidence experiment. Shown are the source of electrons, target gas, tluee electron detectors, one for the scattered electron and one for each of the ejected...

Dupre C, Lahmam-Bennani A and Duguet A 1991 About some experimental aspeots of double and triple ooinoidenoe teohniques to study eleotron impaot double ionizing prooesses Meas. Sol. Technol. 2 327... 

The molecular orbital description of the bonding in NO is similar to that in N2 or CO (p. 927) but with an extra electron in one of the tt antibonding orbitals. This effectively reduces the bond order from 3 to 2.5 and accounts for the fact that the interatomic N 0 distance (115 pm) is intermediate between that in the triple-bonded NO+ (106 pm) and values typical of double-bonded NO species ( 120 pm). It also interprets the very low ionization energy of the molecule (9.25 eV, compared with 15.6 eV for N2, 14.0 eV for CO, and 12.1 eV for O2). Similarly, the notable reluctance of NO to dimerize can be related both to the geometrical distribution of the unpaired electron over the entire molecule and to the fact that dimerization to 0=N—N=0 leaves the total bond order unchanged (2 x 2.5 = 5). When NO condenses to a liquid, partial dimerization occurs, the cis-form being more stable than the trans-. The pure liquid is colourless, not blue as sometimes stated blue samples owe their colour to traces of the intensely coloured N2O3.6O ) Crystalline nitric oxide is also colourless (not blue) when pure, ° and X-ray diffraction data are best interpreted in terms of weak association into... 

Tandem mass spectrometry (MS/MS) is a method for obtaining sequence and structural information by measurement of the mass-to-charge ratios of ionized molecules before and after dissociation reactions within a mass spectrometer which consists essentially of two mass spectrometers in tandem. In the first step, precursor ions are selected for further fragmentation by energy impact and interaction with a collision gas. The generated product ions can be analyzed by a second scan step. MS/MS measurements of peptides can be performed using electrospray or matrix-assisted laser desorption/ionization in combination with triple quadruple, ion trap, quadrupole-TOF (time-of-flight), TOF-TOF or ion cyclotron resonance MS. Tandem... 

APCl in positive mode ionization and triple quadrupole detection was used for determination of free and bound carotenoids in paprika, obtaining the [M + H]+ and losses of fatty acids as neutral molecules from the [M + H]+ with MeOH, MTBE, and H2O as eluent from the C30 column. The positions of the fatty acids on unsymmetrical xanthophylls could not be established by the MS data. 

A triple-quadrupole mass spectrometer with an electrospray interface is recommended for achieving the best sensitivity and selectivity in the quantitative determination of sulfonylurea herbicides. Ion trap mass spectrometers may also be used, but reduced sensitivity may be observed, in addition to more severe matrix suppression due to the increased need for sample concentration or to the space charge effect. Also, we have observed that two parent to daughter transitions cannot be obtained for some of the sulfonylurea compounds when ion traps are used in the MS/MS mode. Most electrospray LC/MS and LC/MS/MS analyses of sulfonylureas have been done in the positive ion mode with acidic HPLC mobile phases. The formation of (M - - H)+ ions in solution and in the gas phase under these conditions is favorable, and fragmentation or formation of undesirable adducts can easily be minimized. Owing to the acid-base nature of these molecules, negative ionization can also be used, with the formation of (M - H) ions at mobile phase pH values of approximately 5-7, but the sensitivity is often reduced as compared with the positive ion mode. 

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