Ion doubly charged ions

The typical SIMS mass spectrum is dominated by singly charged atomic and molecular ions. Doubly charged ions are typically two or more orders of magni-... 

Spectroscopic interferences occur when an ionic species in the plasma has the same m/z values as an analyte ion,, Such interferences fall into four categories (I) iso-baric ions. (2) polyatomic or adduct ions. (. ) doubly charged ions, and (4) refractory oxide ions. ... 

The degree of sophistication of flow tube, drift tube and flow drift tube techniques, especially following the development of selected ion injection sources, is such that now it is possible to study a very wide variety of ion-neutral reactions, including the reactions of state selected ions, doubly-charged ions, weakly-bound (cluster) ions, etc. 

In the past decade there has been photodissociation work on doubly charged positive ions, e.g.,... 

If this concentration is larger than the oxygen vacancies created by thermal effects, then the conductivity from the motion of the doubly charged ions is directly proportional to the concentration of CaO (eq. 15). 

Both the hydroxyl ion (OH)- and the water molecule H20 contain the same number of electrons as a doubly charged oxygen negative ion 0 . 

If we had any means of reducing the electrostatic repulsion without, at the same time, affecting the quantum-mechanical attraction, we should have the possibility of forming such doubly charged molecular ions. Now a polar solvent has just the required properties the alignment of the solvent dipoles greatly reduces the electrostatic repulsion, but the quantum-mechanical forces of attraction arise from the rapid motion of... 

The internal structure of a liquid at a temperature near its freezing point has been discussed in Sec. 24. Each molecule vibrates in a little cage or cell, whose boundaries are provided by the adjacent molecules, as in Fig. 20, and likewise for each solute particle in solution in a solvent near its freezing point. It is clear that the question of the hydration of ions no longer arises in its original form. In aqueous solution an atomic ion will never be in contact with less than three or four water molecules, which in turn will be in contact with other water molecules, and so on. There is an electrostatic attraction, not only between the ion and the molecular dipoles in immediate contact with it, but also between the ion and molecular dipoles that are not in contact with it. For solvent dipoles that are in contact with a small doubly charged ion, such as Ca++,... 

Electrical Conduction by Proton Jumps. As mentioned in Sec. 24, a hydroxyl ion may be regarded as a doubly charged oxygen ion 0 , containing a proton inside the electronic cloud of the ion, which has the same number of electrons as a fluoride ion. The radius of the hydroxyl ion cannot be very different from that of the fluoride ion. But it will be seen from Table 2 that the mobility of the hydroxyl ion is about four times as great. This arises from the fact that a large part of the mobility is undoubtedly due to proton transfers.1 Consider a water molecule in contact with a hydroxyl ion. If a proton jumps from the molecule to the ion,... 

The Electrostatic Energy. In Chapter 2 we drew attention to the fact that, when a proton transfer (117) has been carried out in a solvent, the electrostatic fields of two ions have been created and work must have been done to supply the amount of energy associated with these ionic fields. Let us now compare (117) with the process (123), both in aqueous solution at the same temperature. In both cases an (HaO)+ ion will be formed but in (123), when the proton is removed from the (IIS04)-ion, we have to separate the particles against the mutual attraction of the proton and the doubly charged ion (S04)". Consequently, more work must be done against the electrostatic forces of attraction than in the removal of a proton from a neutral particle. 

Let us consider now the work required to remove the first proton and the second proton. When the doubly charged ion of Fig. 46c has been formed, a certain amount of energy has been put into the electrostatic field of the ion this total amount differs, owing to the proximity of the two negative charges, from twice the amount put into the electrostatic... 

Direct-reading meters suitable for use with ion-selective electrodes are available from a number of manufacturers they are sometimes referred to as ion activity meters. They are very similar in construction to pH meters, and most can in fact be used as a pH meter, but by virtue of the extended range of measurements for which they must be used (anions as well as cations, and doubly charged as well as singly charged ions), the circuitry is necessarily more complex and scale expansion facilities are included. They are commonly used in the millivolt mode. 

Two or more electro-active ions may be determined successively if their half-wave potentials differ by at least 0.4 volt for singly charged ions and 0.2 volt for doubly charged ions provided that the ions are present in approximately equal concentrations. If the concentrations differ considerably, the difference... 

We can now see why nature has adopted an ionic solid, calcium phosphate, for our skeletons the doubly charged small Ca2+ ions and the triply charged P04, ions attract one another very strongly and clump together tightly to form a rigid, insoluble solid (Fig. 2.8)... 

If an ion is doubly charged, wc multiply its concentration by 2 in the charge balance equation, and likewise for triply charged ions. 

Figure 4.20 Product-ion MS-MS spectrum from the doubly charged molecular ion of the peptide glu-fibrinogen B generated during electrospray ionization. From applications literature published by Thermofinnigan, Hemel Hempstead, UK, and reproduced with permission.

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