Spark ionization

O mile," says the photographer, as she pushes a button. The camera shutter opens and an /electric current from a small lithium battery sparks across a gap in the flash unit. This spark ionizes xenon gas, creating a bright flash of light. The energy from the chemical reaction in the lithium battery has been successfully put to use. 

Figure 14.6 Atomic emission instrument with spark ionization. Left, Jobin-Yvon model JY-50. Details of the spark chamber in the open position. Right, mobile post of Metorex ARC Met-900 industrial analysis. The spark is produced by a gun, linked by an optical fibre to the spectrophotometer situated in the console (reproduced courtesy of Jobin-Yvon and American Stress Technologies).

Electrons from a spark are accelerated backward and forward rapidly in the oscillating electromagnetic field and collide with neutral atoms. At atmospheric pressure, the high collision frequency of electrons with atoms induces chaotic electron motion. The electrons gain rapidly in kinetic energy until they have sufficient energy to cause ionization of some gas atoms. 

Spark (source) ionization. Occurs when a solid sample is vaporized and partially ionized by an intermittent electric discharge. Further ionization occurs in the discharge when gaseous atoms and small molecular moieties interact with energetic electrons in the intermittent discharge. It is recommended that the word source be dropped from this term. 

The fundamental parameters in the two main methods of achieving ignition are basically the same. Recent advances in the field of combustion have been in the development of mathematical definitions for some of these parameters. For instance, consider the case of ignition achieved by means of an electric spark, where electrical energy released between electrodes results in the formation of a plasma in which the ionized gas acts as a conductor of electricity. The electrical energy Hberated by the spark is given by equation 2 (1), where V = the potential, V 7 = the current. A 0 = the spark duration, s and t = time, s. 

The electrical energy is rapidly transformed into thermal energy, and because the temperature of the ionized gas is generally above 300 K, the ignition delay time is short compared with the spark duration, . Ignition only takes place if the electrical energy exceeds the critical value, and if this energy is... 

This is a transient discrete electric discharge which takes place between two conductors which are at different potentials, bridging the gap in the form of a single ionization channel (Plate 4). Based on light emission measurements of sparks with symmetrical electrode geometry, the energy is dissipated approximately uniformly along the channel. This is in contrast with asym-... 

Spark Source Mass Spectrometry (SSMS) is a method of trace level analysis—less than 1 part per million atomic (ppma)—in which a solid material, in the form of two conducting electrodes, is vaporized and ionized by a high-voltage radio frequency spark in vacuum. The ions produced from the sample electrodes are accelerated into a mass spectrometer, separated according to their mass-to-charge ratio, and collected for qualitative identification and quantitative analysis. 

The spark source is an energetic ionization process, producing a rich spectrum of multiply charged species (Af/2, Af/3, Af/4, etc.). These masses, falling at halves, thirds, and fourths of the unit mass separation can aid in the positive identification of elements. In Figure 2, species like Au and are labeled. The most abundant... 

Corona discharge Occurs when the field at the tip of the electrode is sufficiently high to ionize the gas surrounding it but insufficiently high to cause a spark. An integral part of the APCl interface. 

Yet another approach is to influence the combustion process itself by ionization, pulsed electromagnetic fields, glow discharge etc. The Institute of Energy at Dnepropetrovsk State University developed a plasma-activated sparking plug, currently in preparation for a full-scale production. 

The intensity of a spectral line is related to the solution concentration of the analyte in a similar complex manner to that described for arc/spark emission (p. 293) although the degree of ionization a will generally be much less... 

Ionization and fragmentation of materials by a variety of means, principally by electron bombardment, or the softer techniques of chemical ionization, field ionization or fast atom bombardment. Analysis of the range of mass fragments produced. Elemental composition of non-volatile materials by application of an RF spark. 

Volatile or volatilizable compounds may be introduced into the spectrometer via a pinhole aperture or molecular leak which allows a steady stream of sample molecules into the ionization area. Non-volatile or thermally labile samples are introduced directly by means of an electrically heated probe inserted through a vacuum lock. Numerous methods of sample ionization are available of which the most important are electron impact (El), chemical ionization (CY), field ionization (FI), field desorption (FD), fast atom bombardment (FAB), and radio-frequency spark discharge. 

Spark source mass spectrometry is used for the examination of non-volatile inorganic samples and residues to determine elemental composition. An RF spark of about 30 kV is passed between two electrodes, one of which may be the sample itself, causing vaporization and ionization. Powdered samples or residues from ashed organic materials can be formed into an electrode after mixing with pure graphite powder. 

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