Electrically excited halogen

The mechanism of action of inhalational anesthetics is unknown. The diversity of chemical structures (inert gas xenon hydrocarbons halogenated hydrocarbons) possessing anesthetic activity appears to rule out involvement of specific receptors. According to one hypothesis, uptake into the hydrophobic interior of the plasmalemma of neurons results in inhibition of electrical excitability and impulse propagation in the brain. This concept would explain the correlation between anesthetic potency and lipophilicity of anesthetic drugs (A). However, an interaction with lipophilic domains of membrane proteins is also conceivable. Anesthetic potency can be expressed in terms of the minimal alveolar concentration (MAC) at which 50% of patients remain immobile following a defined painful stimulus (skin incision). Whereas the poorly lipophilic N2O must be inhaled in high concentrations (>70% of inspired air has to be replaced), much smaller concentrations (<5%) are required in the case of the more lipophilic halothane. 

Since every element possesses characteristic spectra, emission spectroscopy is applicable in both theory and practice to the entire periodic table. However, the emission spectra for some elements, notably halogens and the noble gases, require more energy to produce than do those for a metallic element, and special excitation conditions must be applied. Normally, the emission spectra of all metals and metalloids in a sample occur simultaneously when the sample is electrically excited. 

Quite recently, a class of excimer lasers has been discovered which are pumped by chemical reactions between halogen molecules and excited metastable rare gas atoms. Although these new excimer systems are dependent upon electrical excitation for creation of the metastable atoms and therefore cannot be classified as purely chemical, they nevertheless demonstrate that very high laser-pulse energies at ultraviolet wavelengths can be achieved through chemical reaction. It is safe to predict that excimer systems... 

These experiments show conclusively that the available energy is released almost entirely as internal excitation of the products. The observation that the diatomic product can subsequently excite M atoms electronically demands a degree of excitation which precludes the formation of 2P1/2 halogen atoms, which requires 21.7 kcal/mole (0.94 eV) for I and 10.5 kcal/mole (0.46 eV) for Br. Where electric deflection analysis has been performed [34-36], the averaged rotational energy yield, is about 5 kcal/mole (0.22 eV),... 

When an electric discharge is passed through a cold diatomic gas at low pressure it is partially dissociated into atoms in this way reasonable concentrations of O, H, D, N, halogen or other atoms can be produced in a chemically inert diluent. The recombination of these atoms, and their reaction with other molecules can be observed as the gas flows down a long tube. Many of the reactions produce molecules in excited electronic states the resulting chemiluminescence can be used to measure the concentration of atomic species as a function of distance, and hence time, down the tube. Dr Clyne describes this important technique, which has produced direct measurements of the rates of many exothermic reactions of atoms and free radicals at room temperature and below. The reverse of the recombination steps are, of course, the dissociation reactions whose kinetics at high temperatures were described in the first chapter if the ratio of forward and reverse rate constants is equal to the equilibrium constant, the temperature dependence of these rates can be deduced over very wide ranges of temperature. 

Both solitons and polarons have their characteristic absorption bands below the band gap energy. Then, for the identification of the nonlinear excited states, the optical absorption and the electron spin resonance spectra must be studied, to get information about the midgap states and the spin, respectively. Studies of the electrical properties are also needed to get information about the charge. In this report, the excited states in single crystals of (Pt(en)2][Pt(en) ] 2 4 are studied by the experimental methods mentioned above, and the photo-induced excited state in this material is shown to be polarons, which are also produced by halogen-doping. 

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