Energy distribution in products

As has been noted, the discussion in the preceding two sections only concerns the orbiting cross-section or cross-section for complex formation. These theories cannot predict the relative importance of various exit channels, the energy distribution in products, nor the effect of internal... 

Figure 4.11. Energy distribution in production of HDPE extrusion blow-molded bottles [29].

Inelastic energy transfer processes Instrumental methods for experiments hemical processes at microscopic level photodissociation, energy distribution in products of elementary reactions, reactions of excited species Photodissociation processes, intramolecular processes Dynamics of intramolecular processes... 

The energy distribution in products is usually studied for strongly exothermic elementary reactions. The mean total energy of products for such reactions can be considered to be equal to AC/<> + Eo (see Fig. 4.11). This energy is much higher than the thermal energy Q therefore, we can believe that the energy E released in the reaction products is constant and equal to AI/q +Eo. ... 

The problems of distinguishing H+ produced from H2 by electron impact from the product of dissociative charge transfer reactions between He + and H2 can be studied by determining the kinetic energy distribution in the product H+ (6). The reaction He+ + H2 is exothermic by 6.5 e.v. if the products are atoms or atomic ions. If the reaction is studied with HD substituted for H2, then the maximum kinetic energy that can be deposited in the D + is approximately 2.16 e.v. On the other hand, D + can be produced by electron impact with 5.5 e.v. kinetic energy. If a retarding potential is applied at the repeller in the ion-source of a mass spectrometer, then it is possible to obtain curves related to the kinetic... 

Freed, K.F. and Band, Y.B. (1977). Product energy distributions in the dissociation of polyatomic molecules, in Excited States, Vol. 3, ed. E.C. Lim (Academic Press, New York). 

The translational energy distribution of the product ion in the source (laboratory distribution) is still not what is needed. What is required is the distribution of energy released in the centre-of-mass framework. The conversion of the translational energy distribution in the laboratory framework to the energy release distribution in the centre-of-mass is not a simple exercise [723]. If mean or average energies are considered, however, an expression for conversion from laboratory to centre-of-mass coordinates can be written down [311]. 

Mass spectroscopy is a common detector in crossed-molecular beam experiments and has also been used in flow systems [17]. Measurements are normally restricted to an analysis of the identity of the reaction products and are not sensitive to the internal energy states of the products. The determination of product translational energy distributions in crossed-molecular beam experiments is usually achieved by placing some form of velocity analyser before the mass spectrometer (see below). 

The reaction of OH with Br2 has been studied under crossed-mol-ecular beam conditions [38] and was found to indicate the existence of a stable HOBrBr complex with a lifetime of several rotational periods. The HOBr product translational energy distribution was found to be well described by the RRKM—AM model and to be similar to the OX distribution from the reactions O + Br2 and I2. This is despite the fact that OH is isoelectronic with a F atom and that the most relevant study shows that Cl + Br2 is a direct stripping reaction. The fraction of the total energy appearing in product translation is 36% and there is some indication that the beam source contains a small proportion of vibrationally excited OH which may account for the measured product translational energy distribution extending beyond the maximum allowed for the reaction OH(z> = 0) + Br2. 

The rate of the transformation of reactants into products depends on the amount of energy in the different degrees of freedom of the activated complex. However, the distribution of energy is not a priori known and it is necessary to make an assumption concerning the energy distribution in the degrees of freedom of the activated complex. From the theory of information... 

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