![]() it was his surprisingly simplistic conclusion: if the final state is random, the initial system must have been the opposite, i.e., ordered. ‘Disorder’ in Thermodynamic Entropy Boltzmann’s sense of “increased randomness” as a criterion of the final equilibrium state for a system compared to initial conditions was not wrong.Entropy is also the subject of the Second and Third laws of thermodynamics, which describe the changes in entropy of the universe with respect to the system and surroundings, and the entropy of substances, respectively. ![]() Qualitatively, entropy is simply a measure how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probabilities of a system or in terms of the other thermodynamic quantities. Letters 9, 80 (1971).\)Įntropy is a state function that is often erroneously referred to as the 'state of disorder' of a system. Anderson, Abstracts VII ICPEAC, (North‐Holland, Amsterdam, 1971), p. Los, Abstracts VII ICPEAC, (North‐Holland, Amsterdam, 1971), p. Friedman, Ion‐Molecule Reactions (Wiley‐Interscience, New York, 1970). For a review of reactive scattering of ions and molecules, see E. Karplus, in Molecular Beams and Reaction Kinetics edited by C. VII ICPEAC, (North‐Holland, Amsterdam, 1971). Kuntz, Electronic and Atomic Collisions, Invited Papers. For a review of classical trajectory methods, see D. For a review of quantal treatment of reactive scattering, see J. Letters 10, 2 (1971) Google Scholar CrossrefĪnd (b) R. Levine, in International Review of Science: Theoretical Chemistry (MTP, Oxford, 1972). For a review of theoretical‐computational developments in reactive scattering, see R. Google Scholar Scitation, ISIĪlso, (b) J. Kinsey, in International Review of Science: Reaction Kinetics (MTP, Oxford, 1972). For a review of experimental developments in reactive scattering, see J. Google Scholar Scitation, ISIĪ more recent one is (b) J. Google Scholar Scitation, ISIĪ more recent one is (b) K. A summary of these “derived” translational distributions is given by K. Letters 9, 587 (1971) Google Scholar Crossref An example of an extensive study is that of K. Polanyi, in International Review of Science: Reaction Kinetics (MTP, Oxford, 1962). For a review of recent developments in chemiluminescence, see T. The present analysis is useful for the characterization of both experimental results and theoretical models. The degradation of information by experimental averaging is considered, leading to bounds on the entropy deficiency. The concept of an ``entropy deficiency'' Δ S′, which characterizes the specificity of product state formation, is suggested as a useful measure of the deviance from statistical (``phase‐space dominated'') behavior. The relationship between the information content, the surprisal, and the entropy of the continuous distribution is established, thereby making the link between microscopic collision theory and nonequilibrium statistical mechanics. The essential parameters defining the internal state distribution are isolated, and the information content I( E) of such a distribution (for a microcanonical ensemble) is put on a quantitative basis. It is suggested to represent the energy dependence of global‐type results in the form of square‐faced prism plots (contour maps vs E), and of data for specific‐type experiments (or computer simulations) as triangular‐faced prismatic plots (contour maps vs E). Such contour plots of the yield function Y or the averaged transition probability ω (the ``poor‐man's'' P‐matrix) nevertheless contain the essence of the dynamical results. Many quantal features are thereby lost and the results are often at a level appropriate for comparison with classical calculations (e.g., in the form of low‐resolution contour maps of energy disposal). Moreover, since reactant and/or product state resolution is always experimentally limited (to a greater or lesser degree), data are necessarily coarse‐grained accordingly. The S‐matrix, or reaction probability matrix P( E), ``global'' in nature, contains much more detail than necessary to reproduce the results of any single specific experiment or computer simulation thereof (via classical mechanical trajectory calculations). The present paper considers optimal means of characterizing the distribution of product energy states resulting from reactive collisions of molecules with restricted distributions of initial states, and vice versa, i.e., characterizing the particular reactant state distribution which yields a given set of product states, at a specified total energy E.
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