Ion negative ions

The impact of the fast atoms on the solution surface results in desorption of secondaries (positive ions, negative ions, and neutrals) into the low-pressure gas-phase region above the matrix surface. 

PPNICI. pulsed positive ion/negative ion chemical ionization... 

Negative Ions. Negative ions in flames have been studied less widely than positive ions because they are present in much smaller concentrations typically, n+//i 100. The primary source of negative ions has been suggested (20) to be Reaction 3, comparable to Reaction 4 (see the section on flames with halogen additives). 

Experiment Serum Dilution Positive Ion Negative ion Unique Cpds MurF Hits/ Serum Hits Serum Hits / Total Library... 

MS, Mass spectrometry El, electron impact Cl, chemical ionization MID, multiple ion detection PICI, positive-ion chemical ionization NICI, negative-ion chemical ionization SIM, selected ion nmonitoring TSP, thermospray PPINICI, pulsed positive ion-negative ion chemical ionization ECD, electron-capture detector NPD, nitrogen/phosphorous detector NSTD, nitrogen-selective thermionic detector FT-IR, Fourier transform infrared spectrometry. 

Fig. 4. The ionized regions of the Earth s atmosphere. The F, E and D regions are designated according to the ledges observed in the electron density. Typical altitudinal profiles of the various positive ion densities in the positive ion-electron plrtsma (from Refs.20 and 2I)) are also shown. The negative ion types in the positive ion-negative ion plasma of the lower D-region are known but the detail altitudinal profiles of density are not well characterised and so only the approximate total negative ion density, N, (dashed line) as obtained from Refs.22) and 23) is shown. The profiles of the electron density, Ne, and the total positive ion density, N+, are also included. It is assumed that quasi-neutrality exists throughout the atmosphere, that is Ne N+ in the thermosphere, Ne + N N+ in the mesosphere, and N N+ in the stratosphere and troposphere...

This section discusses these different aspects of positive and negative Ge, Sn and Pb ions. Negative ions have not been discussed in the previous section as they have rarely been used to identify Ge, Sn and Pb compounds103, even though negative ion chemical ionization based on Cl- attachment can often be a useful technique for compounds that display low abundance of the molecular ion in conventional mass spectrometry104. 

Electrodialysis — Figure. The electro dialysis cell (a) [i] (a = anion-permeable membrane c = cation-permeable membrane o = positive ion = negative ion ion migration under action of electrical current (b), causes salt depletion in alternate compartments and salt enrichment in adjacent ones (c))... 

Similar expressions are used for the fluxes of all the species in the system. If the system consists of an electrolyte dissolved in water, one has three species positive ions, negative ions, and water. By using the symbol + for the positive ions, - for the negative ions, and 0 for the water, the fluxes are... 

Figure 7. Comparison of the UV and MS (single-ion, negative-ion, monitoring for m/z 80, RIC) traces for 0.5 nmol of oc2-antiplasmin tryptic digest.

Ionization Sources Several different types of ionization sources are available for molecular mass spectrometry. The most widely used sources are listed in Table 31 -2 One of the most common is the electron impact (El) source. In this source, molecules are bombarded with a high-energy beam of electrons. This produces positive ions, negative ions, and neutral species. The positive ions are directed toward the analyzer by electrostatic repulsion. 

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