Showing papers in "Annual Review of Physical Chemistry in 1973"

Quantum Dynamical Theory of Molecular Collisions

Abstract: The review covers differential and integral equations, mathematical techniques, reduction of the number of coupled equations, Faddeev equations, symmetry effects, and other effects. (JFP)

Chemistry of the Planets

Abstract: Prior to the first Apollo landing on the Moon, man's knowledge of the com­ position of solar system bodies was limited to remote spectroscopic observa­ tions of planetary atmospheres, approximate density determinations of the planets, geochemical and geophysical data on the Earth, and laboratory studies on meteorites. Now we also have in hand hundreds of kilograms of surface samples selected from several widely separated areas on the near side of the moon, and spacecraft investigations of the planets have progressed to the point where instrumented atmospheric entry and landing probes have reached the surfaces of Venus and Mars. This explosion in our knowledge of the composition of solar system bodies, while still in an early stage, nonethe­ less suffices to force a reevaluation of our understanding of the composition, origin, and evolution of the planets, satellites, asteroids, and comets. The crucial questions to which we shall address our attention are:

Equilibrium Isotope Effects

Abstract: Significant theoretical and experimental advances during the past three years in the area of equilibrium isotope effects are reviewed. Section headings are: isotope separation; chemical exchange equilibria: theory; calculations of reduced partition function ratios; chemical exchange equilibria: experimental; solvent isotope effects; isotope effects in phase equilibria; and physical properties of a substance upon isotopic substitution, including heat capacity, phase transitions, superconductivity, and crystalline structure. (248 references) (auth)

Statistical Mechanics of Simple Polar Fluids

Abstract: The field of s tatis tic al mech anics h as received at le as t i ts f ai r sh are of attention from recent issues of the Annual Review of Physical Chemistry. For ex ample the p resent volume contains contribu tions from Alder on compu ter dynamics, Wheele r on cri tic al phenomena, and Egels taff on the li quid s tate. Wi th this excellent cover age in mind I h ave elec ted to p resent a c ri tic al review of a speci al topic in s tatis tic al mech anics of the li quid s tate. This topic, which h as been of interes t to me fo r m any ye ars, is the s truc tu re of simple pol ar fluids. In the l as t three ye ars there h as been a g re at de al of p rog ress in this area and i t seems approp ri ate to p resent a review for the nonspeci alis t. The topic deserves the attention of the nonspeci alis t prim arily bec ause w ate r and o ther pol ar fluids are of such g re at impor tance in nature, cer tainly more so th an the simple r are g as li quids which h ave received so much attention f rom theo ris ts. Of cou rse w ater is a more compl ic ated li quid th an a simple pol ar fluid bec ause of the p resence of hydrogen bonding. On the o ther h and i t seems unlikely th at a successful theo ry of w ate r c an be cons truc ted wi thou t taking into account the essenti al fe atures th at arise when the molecules inter ac t by d ipole-dipole forces. In a si mple li quid the p articles are cus tom arily assu med to inter ac t by p air­ wise addi tive inte rmolecul ar po tenti als u(i, j) [here the argument (i, j) deno tes the posi tion (ft, fj) and o rientation (wj, Wj) of two representative p articles i and j in the fluid]. For a si mple fl uid u(i, j) is assumed to h ave a h ard core fo r which u(i, j) = ex), rjj ::; a, and to be of sho rt range i.e. u(i, j) � 1 rtf 1n wi th n > d whe re d is the dimensionali ty of the sys tem. Mathem atic ally the sho rt r ange condi tion assu res th at the po tenti al is integr able over all sp ace ou tside the h ard co re. Physic ally the condi tion me ans th at the inter ac tion ene rgy of a one­ rep resentative p ar ticle wi th all i ts su rrounding neighbo rs will be fini te and th at 1 Work supported in part by the National Science Foundation and the Alfred P.

The Structure of Simple Liquids

Abstract: The theory of liquids has been reviewed in three recent articles in this series; those of Neece & Widom (1), Berne & Forster (2), and Barker & Henderson (3). These articles describe how in recent years the theory of liquids has made substantial advances and many problems which have been tantalizing workers for the past ten or twenty years have been solved. The consequences of the pair theory of liquids have been worked out and reasonable comparisons made with experimental data on both model and real systems. In the case of the liquified inert gases the field is fairly healthy with general ideas having been successfully developed and fairly satisfactory calculations made in the case of many properties. For simple molecular liquids or liquid metals, the position is less satisfactory but steady progress is being made. Because of the background covered in these three articles the present author will assume the reader is familiar with basic liquid state theory, and he will express his own point of view on current theoretical and experimental situations rather than express an average view. In particular, emphasis will be placed upon the physical ideas involved and the basic merit of a method of calculation. That is, phenomenological treatments will not be regarded as sufficient even where they give exact agreement between calculation and experiment : the view taken is that it is better to obtain approximate agreement via a basic treatment rather than to obtain exact agreement with a phenomenological treatment. Recent methods of discussing the static and dynamic pair correlation functions, and some methods of calculating the diffusion and viscosity coefficients will be considered from the above point of view. The basic hypothesis on which the modern understanding of the behavior of simple liquids is based, is that the short range behavior determines the large range behavior. Thus we suppose that the short distance behavior determines the large distance behavior and the short time behavior determines the long time behavior, and that if we can make a successful "guess" at the short

Chemistry of pollutant formation in flames

Abstract: In Volum� 22 of this series Berry & Lehman (1) presented a critical and stimulating review of the aerochemistry of air pollution. Virtually all of the pollutants discussed there have their origins in combustion processes. We attempt here to supplement that review by examining recent literature on the chemical processes within combustion systems that give rise to those pollutants. The relative importance of the various sources of pollution can be gauged from the data for man-caused pollutant emissions presented in Table I. The

High Speed Liquid Chromatography

Abstract: This review deals with the most rapidly expanding form of chromatographic analysis variously known as high speed, high performance, high pressure, or high efficiency liquid chromatography. The technique which we shall denote by high speed liquid chromatography (HSLC) has arisen from a marriage of classical liquid chromatography and modern gas chromatography. The beginnings of HSLC may be traced to a statement in the classic paper of Martin & Synge (I) of 1941, in which they wrote: "Thus the smallest HETP should be obtainable by using very small particles and a high pressure differ­ ence across the length of the column." Until the late 1960s this recipe for HSLC was l

Dynamical Aspects of Gas-Solid Interactions

Abstract: Surface phenomena continue to attract an ever increasing amount of attention due to technological interest and advances in experimental techniques. The number and variety of review articles has increased significantly. This review will be limited, therefore, to studies of gas surface collisional phenomena in well-defined systems where understanding a dynamical process at the molec­ ular level is of prime concern. As vitally important as they are, techniques for determining surface structure and composition utilizing electron and photon absorption and scattering will not be discussed in detail. A general summary of surface structure determination has been given by Duke & Park (1). Hagstrum (2) has reviewed electronic characterization of surfaces. Optical spectroscopic studies have been reviewed by Jones & Klier (3) and Auger spectroscopy by Somorjai & Szalkowski (4). The general topic of surface analysis has been summarized by Colburn & Kay (5). Surface analysis by ion scattering is receiving increasing attention even though inherent sputtering of the surface limits the applicability (6-11). Recent interest in photoelectron spectroscopy by surface scientists is a reflection of the hope that a surface species spectroscopy can be developed. Other recent reviews dealing with specific surface phenomena include those describing glass surfaces (12), highly dispersed catalytic materials (13), complex chemical reactions on hot surfaces (14, 15) and those appearing periodically in a new review (16). A survey has been given of the various theoretical descriptions of the geometrical, vibrational, and electronic properties of clean surfaces (17).

Artificial Intelligence and Machines that Understand

Abstract: "Can machines be intelligent?" "Can machines think and understand ?" These are questions of epistemology. Since the concepts of intelligence, thinking, and understanding have been thought of until recently only in the context of mental activity in homo sapiens (or other species), these questions should only be asked when we know what we mean by intelligence and thinking, or when we have an "understanding ot 'understanding'. " The formulation in quotes suggests that the fundamental issue associated with these concepts is the epistemology of recursion, that is of concepts being applied to themselves. The issue here is not an isolated case, as indicated by the numerous attempts to grasp the logic of self-referring concepts (1), for instance self-reproduction (the reproduction of reproduction) (2), self-explanation (the explanation of explanation) (3), autonomy, i.e. self-regulation (the regulation of regulation) (4, 5), and many more. Although considerable progress has been made along these lines of inquiry, the last word has not yet been spoken. Nevertheless, by virtue of the paraphrase as suggested above, we may at least find out whether or not we are in principle able today to answer the questions with which we opened this paragraph by asking" Do we understand ourselves?" The answer to this is an undeniable "No." Moreover, the problem of whether in principle an affirmative answer to: "Can we understand ourselves?" will ever be found is still a logicoepistemic problem (6-8). "Can machines complement our intelligence, thinking, and understanding?" This question is practical, and its answer is an undeniable "Yes." In this formulation the question circumvents logical absurdities that arise by reference to artifacts with "mind-like" behavior or to computer programs which "simulate" mental activity, for how are we to know that we have succeeded in rendering the likeness of something that is in itself not known? Moreover, this question avoids semantic monstrosities that arise by reference to machines

Reactions of High Kinetic Energy Species

Abstract: Significant advances made during the past ten years are discussed under the following section headings: sources of high kinetic energy species, including bulb techniques and molecular beams; reactivity--excitation functions, including reactions with negligible energy barriers, reactions with energy barriers, excitation functions in the absence of reactant vibrational excitation, and energy dependence in the presence of reactant vibrational excitation; microscopic mechanisms; direct reactions, including high energy stripping modes and simple exchange reactions; hot atom chemistry of atomic tritium, including general features, substitution reaction, models, and prognosis-nuclear recoil studies. (103 references) (JGB)

Optical Properties of Polymers

Abstract: Many optical properties of solid polymers such as their spectra do not differ from those of low molecular weight solids and these are not reviewed here. We concern ourselves with those properties which differ because of the polymeric nature of the system. These are of two types: 1. Those which depend upon anisotropy and arise from the possibility of long range orientation for polymeric systems, and 2. those which depend upon interference effects arising from the large size of polymers. Properties of the first type include birefringence, infrared dichroism, Raman polarization, and fluorescence polarization, while those of the latter type involve light and X-ray scattering. In addition we concern our­ selves with the application of dynamic optical studies for learning about the time dependence of structural changes that may be studied by optical means.

Status Report on Critical Compilation of Physical Chemical Data

Abstract: The late Farrington Daniels dncc defined physical chemistry as "the study of interesting things." While this is perhaps a slight overstatement of the eclectic interests of physical chemists, it is fair to say that no other group of scientists has a stronger tradition of ignoring rigid disciplinary boundaries. Thus, the term "physical chemical data" must be interpreted very broadly; it is difficult to think of measurable properties that are not of interest to some physical chemists. In this review we use the word "data" to mean quantitative values' of well­ defined properties (in the context of accepted physical theories) of well­ characterized systems. Thus, we include all the customary physical and chemical properties of pure substances and mixtures of known composition. We exclude from consideration poorly characterized natural products (coal, petroleum), large natural systems (earth, solar system), and living organisms. Whatever the motivation of a particular experimental research effort in physical chemistry, one of the outputs is usually a set of numerical data. When the results of the research are published, the most immediate impact of the paper may derive from a new physical insight, test of a theory, or suggestion for further experiments. In the long term, however, the experimental data contained in the paper are likely to find uses that could not have been antici­ pated by the original research workers. Such data, if carefully measured and documented, form a reservoir of great value to the progress of science. The retrieval, organization, and screening of these data from the primary research literature has been recognized as an important task since the beginning' of modern science. The exponential growth of the literature during the last 25 years has accentuated a problem that was already apparent a century ago.

Physical Chemistry in Cambridge, Massachusetts

Abstract: s. The activities in physical chemistry past the \"Early Days\" expanded and diversified, so that it is more convenient to discuss the later years by subject matter categories.

The Structural Chemistry of Extended Defects

Abstract: Studies on the characterization of extended defects are reviewed under the following section headings: structures based on crystallographic shear, including crystallographic shear and shear vectors, one-dimensional crystallographic shear (shear in molybdenum and tungsten trioxides and rutile), two-dimensional crystallographic shear, and disordered crystallographic shear; and, the fluorite-related structures, including the relationship between the fluorite and other structures ( alpha -UO/sub 3/, CaF/sub 2/, La/sub 2/O /sub 3/, and Sm/sub2/O/sub 3/), the fluorite-related homologous series, and disordered fluorite-related phases. (120 references) (JGB)