Types of Ions Produced

Types of Ions Produced  [c.86]

A large number of ordered surface structures can be produced experimentally on single-crystal surfaces, especially with adsorbates [H]. There are also many disordered surfaces. Ordering is driven by the interactions between atoms, ions or molecules in the surface region. These forces can be of various types covalent, ionic, van der Waals, etc and there can be a mix of such types of interaction, not only within a given bond, but also from bond to bond in the same surface. A surface could, for instance, consist of a bulk material with one type of internal bonding (say, ionic). It may be covered with an overlayer of molecules with a different type of intramolecular bonding (typically covalent) and the molecules may be held to the substrate by yet another fomi of bond (e.g., van der Waals).  [c.1758]

Both types of multipoint array are particularly useful for detecting ions produced either from a very small amount of a substance or when ionization is not continuous but intermittent.  [c.410]

After the analyzer of a mass spectrometer has dispersed a beam of ions in space or in time according to their various m/z values, they can be collected by a planar assembly of small electron multipliers. There are two types of multipoint planar collectors an array is used in the case of spatial separation, and a microchannel plate is used in the case of temporal separation. With both multipoint assemblies, all ions over a specified mass range are detected at the same time, or apparently at the same time, giving these assemblies distinct advantages over the single-point collector in the analysis of very small quantities of a substance or where ions are produced intermittently during short time intervals.  [c.410]

The implantation system shown in Figure 2 illustrates a conventional ion implantation system in widespread use within the semiconductor industry. Using different types of available ion sources, a wide variety of beams can be produced with sufficient intensity for implantation processes required for integrated circuit technology. For semiconductors, a representative ion dose is -10 ions/cm (metallurgical appHcations generally require doses from 10 -10 ions/cm ). This system produces a unidirectional beam and, in this article, is referred to as a directed beam system. A mass-separating magnet (for mass analysis) is almost mandatory for semiconductor processing in order to eliminate unwanted species that often contaminate the extracted beam. However, for metallurgical processing, mass separation is not important and, as a result, the basic instmmentation can be quite simple.  [c.390]

If the products of electrolysis favor other types of corrosion, electrochemical protection processes should not be applied or should be used only in a limited form. Hydrogen and OH ions are produced in cathodic protection according to Eq. (2-19). The following possible corrosion danger must be heeded  [c.70]

Raman spectra of solid solutions, crystals with lattice defects, and systems having other types of structural disorder usually exhibit a pronounced line broadening in comparison with ordered structures. Structural defects, such as lattice vacancies, produce line broadening with little temperature dependence. Orientational disorder, arising from alternative possible orientations of molecules in crystals, dipoles in highly polar crystals, and nonbonding lone pair electrons in ions like Pb and As, produce Raman lines that are broad at room temperature but become narrow as temperatures are lowered into the liquid nitrogen or liquid helium range. At high defect concentrations, greater than 10-20% mole, the broadened Raman lines give way to a scattering continuum having little structure.  [c.437]

Chain polymerization involves at least two steps initiation, i.e. fonnation of reactive sites, which are generally radicals or ions and propagation, tlirough which tire chains grow. In most practical conditions tennination reactions play an important role. Depropagation, i.e. tire reduction of tire degree of polymerization by one unit is also possible. In tennination reactions, one or two reactive sites vanish and chain growtli is stopped. The possibility of growtli tennination of a chain exists at every addition step and, tlierefore, tire probability of tennination increases witli tire degree of polymerization. This increase leads to tire flattening of tire average molecular weight as a function of tire degree of monomer conversion, as shown in figure C2.1.3 [5]. In tire limiting situation of fast initiation, irreversible propagation and tire absence of tennination, tire molecular weight increases linearly witli tire degree of conversion (figure C2.1.3). These conditions are approached in some ionic chain polymerizations perfonned under very clean conditions. Such reactions are called living polymerizations. Radical chain polymerization and also many chain polymerizations witli simple ions as reactive sites produce polymers witli irregular configuration. To prepare highly-regular polymers special catalysts have been developed. Two types widely used are Ziegler—Natta catalysts [6] and metallocene-based catalysts [7].  [c.2515]

To simplify oil sample spectra, data is obtained using low energy (<10 eV) electron ionization. This minimizes fragmentation and gives spectra containing mainly molecular ions (65), but there is stiU a significant amount of data to analyze (66). The geographic origin of an oil sample can be deduced from the types and abundances of steranes it contains (67). Sterane distributions have been determined by using ms /ms to monitor fragmentation of the sterane molecular ions which produces the characteristic ion of ml 217 or by high resolution monitoring of m 217 (68).  [c.548]

Modem phosphating practice involves the treatment of reactive metals with acidic phosphate-containing solutions. This produces a coating which consists mainly of phosphate compounds. Chemically, phosphating processes can be separated into two types. In processes of the first type, the metal ions of the phosphate layer derive almost totally from the substrate. These layers, known as noncoating or iron phosphates, are based on sodium and ammonium dihydrogen phosphate. Processes of the second type, on the other hand, provide metal ions for coating either partially or totally in the phosphate bath. These are the zinc phosphate processes which may contain zinc alone or modifying ions such as nickel, manganese, calcium, as well as several others.  [c.222]

Latex Properties. Almost all latex concentrates ate produced to meet an international standard, ISO 2004 (Table 11). This standard gives minimum requirements for mbbet content and sets limits on some other latex properties. One of the most important properties is mechanical stabiHty, which gives an indication of the resistance to flocculation or coagulation during processing of the latex. Mechanical stabiHty rises naturally, particularly during the first month after concentration, owing to the chemical action of ammonia on some latex compounds (65). It can also be raised artificially by the addition of soaps to the latex. Copper and manganese concentrations ate limited because of the severe degrading effects of these metals on finished products. The volatile fatty acid (VEA) number gives an indication of bacterial activity and thus shows how weU the latex has been preserved (66). This is a particularly important test for low ammonia latices, which have no minimum requirement for ammonia content. Eot all five types in Table 11, the VEA specification (ISO 506) is as agreed by the interested patties, but not to exceed 0.20. The KOH number (ISO 127) for all five types is as agreed by the interested patties, but not to exceed 1.0. If the latex contains boric acid, the KOH number may exceed the specified value by an amount equivalent to the boric acid content as deterrnined according to the method specified in ISO 1802. Color and odor specification ate as foUows on visual inspection there should be no pronounced blue or gray and after neutralization with boric acid, there should be no pronounced odor of putrefaction. The most important latex properties not coveted by ISO 2004 ate latex viscosity, magnesium content, and stabiHty in the presence of zinc ions (67,68).  [c.273]

The ion engine produces a t cry tiny thrust, about the weight of a sheet of typing paper, but exerts it continuously for a long period of time (several months). This very long time multiplied by the relatively small thrust (force) still results in large impulse to the space probe. Because it is not possible to push more xenon ions through the engine in a given time only low thrust is possible. Greater thrust would require a much larger engine and a more powerful source of energy.  [c.968]

Various bacteria are involved in corrosion processes. Of these, the most important are some Thiobacillus types (these generate sulfuric acid which dissolves concrete) and sulfate-reducing bacteria (SRB). SRB are ubiquitous but only create significant corrosion problems in conditions suitable for rapid growth. They flourish best in anaerobic conditions, with a supply of sulfate ions and a carbon source. Anaerobic conditions are created in stagnant areas of chemical plant, under slime in industrial cooling systems and soils and seabed mud. Sulfate ions are widely available, especially in the sea and some chemical processes. Suitable carbon sources include organic materials such as acetic acid. SRB produce sulfide ions from sulfate ions. In conditions such as beneath a colony of these bacteria corrosion processes as illustrated in Figure 53.5 occur. Many metals are susceptible to this form of attack, including steel, stainless steels, copper alloys and aluminum alloys. Localized pitting rates in excess of 10 millimeters per year are possible on steel in some circumstances. Some Cladosporium fungi cause pitting attack on aluminum alloys. Gallionella bacteria thrive in solutions containing Fe + and produce deposits under which anaerobic processes can occur.  [c.894]

LIMS uses a finely focused ultraviolet (UV) laser pulse (-lO ns) to vaporize and ionize a microvolume of material. The ions produced by the laser pulse are accelerated into a time-of-flight mass spectrometer, where they are analyzed according to mass and signal intensity. Each laser shot produces a complete mass spectrum, typically covering the rai e 0—250 amu. The interaction of laser radiation with solid matter depends significantly upon the duration of the pulse and the power density levels achieved during the pulse. When the energy radiated into the material signif-icandy exceeds its heat of vaporization, a plasma (ionized vapor) cloud forms above the region of impact. The interaction of the laser light with the plasma cloud further enhances the transfer of eneigy to the sample material. As a consequence, various types of ions are formed from the irradiated area, mainly through a process called nonresonant multiphoton ionization (NRMPI). The relative abundances of the ions are a function of the laser s power density and the optical properties and chemical state of the material. Typically, the ion species observed in LIMS include singly charged elemental ions, elemental cluster ions (for example, the abundant negative ions observed in the analysis of organic substances), and organic fragment ions. Multiply charged ions are rarely observed, which sets an approximate upper limit on the energy that is effectively transferred to the material.  [c.587]

Strictly speaking, die temi absorption spectroscopy refers to iiieasurements of light intensity. In practice, the absorption may be deduced from the detection of electrons or ions produced in the process, such as in absorption of light leading to pliotodetachment or photodissociation, i.e., action spectra. In the absorption spectroscopy of ions, this is a natural tack to take as the charged-particle production can be detected with greater precision than is possible for a measurement of a small change in the light intensity. The most important of such experiment types is the coaxial beams spectrometer, one of which is described in detail in the section on dissociation of ions. In these experiments, the ions are identified by mass and collimated, and interact with the laser beam over a long distance (0.25-1 in). The method was first used with ions in 1976 for HD, with the absorption events detected via eidianced production of buffer gas ions as a result of charge  [c.805]

Ions produced in an ion source can be separated into their m/z values by a variety of analyzers. The resultant set of m/z values, along with the numbers (abundances) of ions, forms the mass spectrum. The separation of ions into their individual m/z values has been effected by analyzers utilizing magnetic fields or RF (radio frequency) electric fields. For example, the mass analysis of ions by instruments using a magnetic field is well known, as are instruments having quadru-pole RF electric fields (quadrupole, ion trap). Ions can also be dispersed in time, so their m/z values are measured according to their flight times in a time-of-flight (TOF) instrument. These individual pieces of equipment have their own characteristics and are commonly used in mass spectrometry. In addition, combinations of sectors have given rise to hybrid instruments. The earliest of these was the double-focusing mass spectrometer having an electric. sector to focus ions according to their energies and then a magnetic sector to separate the individual m/z values. There is now a whole series of hybrid types, each with some advantage over nonhybrids. Ion collectors have seen a similar improvement in performance, and any of the above analyzers may be used with ion detectors based on single-electron multipliers or, in the case of magnetic sectors, on arrays of multipliers, or, in the case of ion cyclotron resonance (ICR), on electric-field frequencies.  [c.195]

In 1893 at the age of 26, Alfred Werner produced his classic coordination theory/ It is said that, after a dream which crystallized his ideas, he set down his views and by midday had written the paper which was the starting point for work which culminated in the award of the Nobel Prize for Chemistry in 1913. The main thesis of his argument was that metals possess two types of valency, (i) the primary, or ionizable, valency which must be satisfied by negative ions and is what is now referred to as the oxidation state and (ii) the secondary valency which has fixed directions with respect to the central metal and can be satisfied by either negative ions or neutral molecules. This is the basis for the various stereochemistries found amongst coordination compounds. Without the armoury of physical methods available to the modem chemist, in particular X-ray crystallography, the early workers were obliged to rely on purely chemical methods to identify the more important of these stereochemistries. They did this during the next 20 y or so, mainly by preparing vast numbers of complexes of various metals of such stoichiometry that the number of isomers which could be produced would distinguish between alternative stereochemistries.  [c.912]

Black chromium plating Black chromium deposits are frequently required for the optical and instrument industries. The deposits contain large amounts of chromium oxides and are not strictly speaking chromium deposits. Graham recommends a solution consisting of 250 g/1 of chromic acid, 0-25 g/1 of hydrofluosilicic acid and a CrOj H2SiFj ratio of 1 000 1. The bath is operated at about 32°C with a current density of about 30 A/dm and a bath voltage of 6 V. The electrolyte solution must be free from sulphuric acid, excess sulphate ions being removed by treatment with barium sulphate. Silvery deposits of chromium containing some nickel are obtained at 70-100 A/dm from a bath consisting of 200 g/1 of chromic acid, 20g/1 of nickel chloride and 5ml/l of glacial acetic acid. By a short immersion (5-30 s) in concentrated hydrochloric acid, the deposit becomes greyish black. Good black deposits are produced from a bath containing 200g/1 of chromic acid, 20g/1 of ammonium vanadate and 6-5ml/l of glacial acetic acid at a current density of 95 A/dm and a temperature of 35-50°C . Some types of black chromium deposits are claimed to have very good corrosion resistance.  [c.548]

In this process a photohole,, and a reduction-sensitization center combine to produce two interstitial silver ions, Ag", and a conduction band electron, e/g. AH of these products are reactants in the latent-image forming process and thus can impact favorably on photographic efficiency. However, reduction treatment of any of these types must be controlled carefully because excessive chemical reduction may produce atomic silver centers of sufficient size or activity to catalyze spontaneous development (sensitization fog). Such oversensitization can reduce sensitivity and increase the developed density in the unexposed regions of negative films. The controlled use of iodide to produce hole traps and/or as a means to estabUsh phase boundaries which can encourage electron—hole separation has contributed significantly to the sensitivity advantages of commercial tabular grains (147,211).  [c.448]

Species other than protons and inorganic ions are also transported across certain membranes by specialized ATPases. Yeast Saccharomyces cerevisiac) has one such system. Yeasts exist in two haploid mating types, designated a and a. Each mating type produces a mating factor (a-factor or n-factor, respectively) and responds to the mating factor of the opposite type. The a-factor is a peptide that is inserted into the ER during translation on the ribosome. a-Factor is glycosylated in the ER and then secreted from the cell. On the other hand, the  [c.307]

Saline particles These are of two main types. The first is ammonium sulphate formed in heavily industrialised areas where appreciable concentrations of ammonia and SOj or of H2SO4 aerosol co-exist. It is a strong stimulator of the initiation of corrosion, being hygroscopic and acidic. The second is marine salt, mainly sodium chloride but quite appreciable quantities of potassium, magnesium and calcium ions are analysed in rainfall Chlorides are also produced in industrial areas and for the UK the fall-ofl in concentration of marine salt with distance from the sea is partially masked by chloride produced by the industrial regions in the centre of the country . Chlorides are also hygroscopic and the chloride ion is highly aggressive to some metals, e.g. stainless steel.  [c.339]

See pages that mention the term Types of Ions Produced : [c.811]    [c.446]    [c.963]    [c.1280]    [c.1046]    [c.1218]    [c.732]   
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Mass Spectrometry Basics  -> Types of Ions Produced