Excitation effects

Elfccts similar to recoil effects arc observed if nuclei arc bombarded with high-energy projectiles. The momentum transmitted to the target nucleus results in a kinetic energy given by 

Electron shells arc influenced by mono- or binuclear reactions in various ways  

These effects overlap and lead to ionization, emission of electrons from the electron shell and fluorescence. They may cause secondary reactions in molecules and subsequent reactions of the ions or excited atoms or molecules produced by these effects. 

If a nucleus suffers a recoil, parts of the electron shell, in particular valence electrons, may be stripped off and stay behind, resulting in ionization of the atom. This ionization depends on the recoil energy, the strength of the chemical bonds and the state of matter. Ions carrying from 1 to about 20 positive charges have been observed. 

Alpha decay leads to a decrease of the atomic number by two units, Z — Z — 2, and causes an expansion of the electron shell, as illustrated in Fig. 9.5 for the a decay of radioisotopes of Bi. EHffercnccs in the binding energies arc marked for electrons in the inner shells. Furthermore, there arc two surplus electrons after a decay. However, in the case of a decay the excitation effects due to the change of the atomic number are relatively small compared with the recoil effects that have been discussed in the previous section, with the result that the recoil effects dominate. 

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Exciting effect. The minimal dose inducing signs of exciting action in at least 2 out of 5 cats. 

Sama of drug Toxicity COQVUl- sant Action General Lepres- 6iOQ Anal-ge sle Exciting Effect Emetic Action Respi- ratory Effect... 

There is also a process called asynchronous excitation, in which the autoperiodic oscillation is released by means of the heteroperiodic one. It might seem that these asynchronous effects were the same that in the quenching effect the autoperiodic oscillation is suppressed while in the excitation effect, it is released. In reality this conclusion is more apparent than real, since in the quenching effect the only requirement is that to should be large enough, while in the excitation effect to may have any value and what counts is the character of the function f (x,x) in Eq. (6-148). 

Tepper, J.M. Nakamura, S. Young, S.J. and Groves, P.M. Autoreceptor-mediated changes in dopaminergic terminal excitability Effects of striatal drug infusions. Brain Res 309 317-333, 1984. 

Bell. J. A., and Matsumiya, T. (1981) Inhibitory effects of dorsal horn and excitant effects of ventral horn intraspinal microinjection of norepinephrine and serotonin in the cat. Life Sci., 29 1507-1514. 

Mode of action of opioids. Most neurons react to opioids with hyperpolarization, reflecting an increase in 1C conductance. Ca influx into nerve terminals during excitation is decreased, leading to a decreased release of excitatory transmitters and decreased synaptic activity (A), Depending on the cell population affected, this synaptic inhibition translates into a depressant or excitant effect (B),... 

Electron damage and electronic excitation effects. Electron bombardment heating is suitable for the evaporation of all metals under vacuum, but its use in metal vapor synthesis can create problems because of electrons interacting with substrate molecules to form product-destroying ions or radicals. Electron... 

Fig. 2.15 (a) In low temperature pulsed-laser field evaporation of silicon, ions formed are all doubly charged. The energy distributions are very narrow, similar to those found in low temperature field evaporation of metals. However, the onset flight times are always shorter than the calculated values, indicating a photo-excitation effect as will be discussed in Sec.2.2.6. 

To date, neither PAH emission nor absorption has been detected in the circumstellar envelope around a cool carbon star PAH emission has only been seen in carbon-rich environments where there is substantial energy density of ultraviolet radiation. This correlation could simply be an excitation effect the carbon features are only excited by the presence of ultraviolet radiation. However, it could also be that carbon particles are eroded into PAHs in the environment where ultraviolet penetrates either directly by the ultraviolet radiation or indirectly by shocks that accompany the radiation. 

Deriving an abundance from the observed lines should be straightforward. However, corrections must be applied to compensate for excitation effects. 

General theory of laser-induced quantum beats. II. Sequental laser excitation effects of external static fields, Phys. Rev. A, 18, 1517-1528. 

Recently the number of papers about radiation effects of ion beams on polymers has been increasing very rapidly both in the fundamental and applied fields. A fairly large number of papers have been published on the fundamental aspects of radiation effects of ion beams on polymers, including high density electronic excitation effects [1, 2]. A number of papers have been published on the more applied aspects of the ion beam assisted advanced science and technology of polymers examples of these are ion beam modification [1. 2] and lithography [3],... 

Carbonization is one of the most drastic phenomena of electronic excitation effects induced by ion beams [1, 2]. The mechanisms of carbonization and the chemical structure of the carbon-rich layer are still controversial problems. Many spectroscopic techniques have been applied to studies of carbonization such as RBS [14], Raman [14], IR [15], ESR [16], ESCA [17], electron microscope [18, 19] and electron energy loss spectroscopy in normal and reflection mode [20]. 

With carbonization, coloration of the polymers occurs [21]. Mechanisms of coloration or blackening of polymers induced by ion beams have been studied [22, 23] and two different models of blackening processes have been proposed direct knock-on of atoms from polymer chains by nuclear collision [22] and high density electronic excitation effects by an electronic excitation process [23]. 

Ion beam induced ablation is one of the most important electronic excitation effects [1,2]. Ablation phenomena occur both thermally and photochemically in many kinds of materials including polymers and biological systems irradiated by both ion beams and high power laser pulses. The mechanisms of ablation of polymers induced by high density electronic excitation have not been made clear yet. 

The application of ion beams to polymers has been worthy of remark in the fields of advanced science and technology since the radiation effects of ion beams on polymers are different from those of conventional radiation such as electron beams and gamma-rays. The effects of ion beams are called LET effects but the detailed mechanisms of these effects on polymers have not been elucidated so far. So-called high density excitation effects such as carbonization, blackening, ablation and formation of nuclear tracks, which only occur at high densities, have been studied by a number of advanced spectroscopic methods. 

Very recently LET effects of ion beams on both standard polymers such as polystyrene and low molecular polyethylene model compounds (n-alkanes) have been studied by time-resolved spectroscopic methods, that is, ion beam pulse radiolysis techniques. Further basic studies are necessary so that the detailed mechanisms of ion beams on polymers can be clarified, especially LET effects and high density excitation effects. 

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