Particle, charged secondary

Other characteristics of particles that influence their deposition are density, charge, shape, solubility, and hygroscopicity. These play a secondary role to particle size. The density of the particle contributes to its mass and, thus, inertia [20,23]. Increasing density will result in increased, or more rapid, deposition of particles. Charge has a number of effects. First, particles may aggregate as... 

The main components of a secondary ion mass spectrometer are the primary particle source (charged bombarding particles), the secondary ion source (containing the bombarded target with the sample molecules M on its surface), the e/m analyser, and the ion detection unit, see Scheme 4.1. 

The charge on a droplet surface produces a repulsive barrier to coalescence into the London-van der Waals primary attractive minimum (see Section VI-4). If the droplet size is appropriate, a secondary minimum exists outside the repulsive barrier as illustrated by DLVO calculations shown in Fig. XIV-6 (see also Refs. 36-38). Here the influence of pH on the repulsive barrier between n-hexadecane drops is shown in Fig. XIV-6a, while the secondary minimum is enlarged in Fig. XIV-6b [39]. The inset to the figures contains t,. the coalescence time. Emulsion particles may flocculate into the secondary minimum without further coalescence. 

Ions impacting onto the cathode during a discharge cause secondary electrons and other charged and neutral species from the electrode material to be ejected. Some of these other particles derived... 

Static SIMS entails the bombardment of a sample surface with an energetic beam of particles, resulting in the emission of surface atoms and clusters. These ejected species subsequendy become either positively or negatively charged and are referred to as secondary ions. The secondary ions are the actual analytical signal in SIMS. A mass spectrometer is used to separate the secondary ions with respect to their charge-to-mass ratios. The atomic ions give an elemental identification (see... 

Physically the generation of X-rays is often a secondary process preceded hy the ionization of an atom. There are, therefore, several possihilities of X-ray generation depending on the type of the exciting medium - neutrals or charged particles such as electrons and ions and high-energy photons, i. e. X-rays themselves. 

An IBSCA-spectrum (Fig. 4.48) consists of many peaks in the visible range (250-900 nm). Every peak can be related to an process of electron de-excitation of a sputtered particle from a higher to a lower state, for the more dominant peaks to the ground state. There are, in principle, two major types of peak family type I - photons emitted from excited sputtered secondary neutrals and type II - photons emitted from excited sputtered secondary ions (single charged). 

As two particles approach in a liquid their charge fields may interact and form two minima as depicted in Figure 6.8. If the particles approach to a distance Li, known as the primary minimum they aggregate to form a configuration with minimum energy - and rapid coagulation is said to take place. On the other hand, if the particles remain separated at a distance L2, the secondary minimum, loose clusters form which do not touch. This is known as slow coagulation and is the more easily reversed. 

Nitmerotts examples of chmbing the ladder can be fotmd in textbooks for secondary edncation. For example, textbooks start the stndy of the snbject of salts with the (strb-) microscopic particles of atoms and molectrles, followed by how atoms theoretically ate converted into iotts, and how ionic srrbstances ate brrilt from charged ions. Textbooks continne with the macroscopic properly of the soln-bility of ionic snbstances in water. Snbseqnently mote complex ions, snch as strl-phates and nitrates, ate addressed to become part of the stndents repertoire ns-ing the sub-microscopic world of chemistry and the symbolic representations. For other subjects, such as organic chemistiy, the pathway for stndy from the basic sub-microscopic particles and related chemical principles to making sense of a relevant macro-world of applications (e.g. production of medicines) is very long. Moreover, the sub-microscopic world of state-of-the-art chemistry has become very complex. 

Verwey and Hamaker (10) have modified the Morse curve to take into account the approach of two charged bodies, as shown in Figure 4. Here, as one moves outward toward increasing distance of separation, an electrostatic repulsion is encountered because the charges are similar. A secondary minimum is then encountered as a result of the concentration of counter ions around each charged particle. The shallowness of the secondary minimum shows that the deflocculated system is metastable. The importance of the Verwey and Hamaker concept lies in its ability to show graphically the correlation between the secondary minimum and the metastable position. A, Figure 1. 

This book lays emphasis on the fundamental aspects of the chemical consequences of charged particle interactions with matter, particularly in the condensed phase. No details will be given about experimental apparatus or procedure, but results of experiments are discussed in relation to theoretical models. The role of the electron both as a radiation (primary and secondary) and as a reactant has been fully treated. Wherever necessary, physical theories have been discussed in detail with understanding of radiation-chemical experiments in view. 

The electron itself is frequently used as a primary source of radiation, various kinds of accelerators being available for that purpose. Particularly important are pulsed electron sources, such as the nanosecond and picosecond pulse radiolysis machines, which allow very fast radiation-induced reactions to be studied (Tabata et al, 1991). Note that secondary electron radiation always constitutes a significant part of energy transferred by heavy charged particles. For these reasons, the electron occupies a central role in radiation chemistry. 

Chemical dosimeters measure the absorbed dose by the quantitative determination of chemical change—that is, the G value of a suitable product—in a known chemical system. These are secondary dosimeters in the sense that the corresponding G values must be established with reference to a primary, absolute dosimeter. The primary dosimeters are usually physical in nature calorimeters, ionization chambers, or charge measuring devices with particles of known energy. However, the primary dosimeters are generally cumbersome, whereas the chemical dosimeters are convenient to handle. On the other hand, the chemical dosimeters are not suitable for low-dose measurements. 

To be able to detect a single particle, the number of ions produced must be increased. As voltage is increased into the proportional region, the primary ions acquire enough energy to cause secondary ionizations (gas amplification) and increase the charge collected. These secondary ionizations may cause further ionization. 

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