Showing papers on "Cluster (physics) published in 1969"
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TL;DR: Field Ion Microscope Observations of Cluster Formation in Metal Deposits on Tungsten Surfaces (FIMMS) as mentioned in this paper...,.. ]..
Abstract: Field Ion Microscope Observations of Cluster Formation in Metal Deposits on Tungsten Surfaces
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TL;DR: In this article, a semi-empirical method for determining the hydrogen bond energy for water clusters in the vapor phase is given, based on a general statistical-mechanical theory of clustering.
Abstract: A simple semiempirical method is given for determining the hydrogen bond energy for water clusters in the vapor phase. This method is based on a general statistical‐mechanical theory of clustering. The partition function for a system of clusters is used to determine the equilibrium distribution of clusters. In conjunction with available thermodynamic and spectroscopic data, the cluster equilibrium constants can be used to calculate the cluster potential energy and the hydrogen bond energy. Results for the water dimer agree quite well with other reported values obtained either by quantum‐mechanical calculations or approximate thermodynamic estimates. A correct temperature dependence of the bond energies is found.
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TL;DR: In this paper, the growth and decay of physical clusters are described by simple models of energy exchange between degrees of freedom at a common temperature, and the reaction probabilities are obtained from the phase integrals for critical energy configurations, neglecting cross terms in the Hamiltonian.
Abstract: It is attempted to calculate the course of homogeneous condensation in a classical monatomic vapour from molecular rather than thermodynamic precepts. The growth and decay of physical clusters is described by simple models of energy exchange between degrees of freedom at a common temperature. Unimolecular and bimolecular reaction probabilities are obtained from the phase integrals for critical energy configurations, neglecting cross-terms in the Hamiltonian. Hard-sphere collision diameters and zero-temperature pair energies are introduced as parameters in place of potential functions. Two-atom clusters (dimers) form and decay by special mechanisms involving weak interaction with atoms of a permanent gas. Detailed balance yields size distributions of the Volmer kind. These either converge and are stable, or diverge above a certain size and are metastable. Examples are given for argon. Saturation pressures are calculable from parameters. Surface tension causes the minima in metastable curves and is calculated for argon clusters of up to ten atoms. The non-equilibrium problem is partially solved for distributions not too close to thermodynamic states. No information on the trans-critical sizes results, but concentrations at smaller sizes are found in terms of characteristic times. The threshold phenomenon is connected with the structure of growing clusters, confirming Volmer's conclusion. The behaviour after onset requires further investigation with a theory of the parameters.
TL;DR: In this paper, the existence of the anions [Rh7(CO)16]3, [Rh6( CO)14]4, and [Rh3(Co)10] was shown.
Abstract: Chemical evidence is presented for the existence of the anions [Rh7(CO)16]3–, [Rh6(CO)14]4–, and [Rh3(CO)10]–.
TL;DR: In this article, the main properties of such levels, which are consequences of their cluster structure, are discussed, and arguments are adduced to sustain the assumption that nuclei at high excitation energies should have systems of cluster levels, connected with some thresholds of two-body break-up.
TL;DR: An efficient computer method which uses an extension of the familiar gravitational field to find clusters of multidimensional data is suggested, and the manipulation of a single parameter permits one's perspective of the data to range from the locally sensitive to the globally sensitive.
TL;DR: It is safe to say that a fully satisfying theory of medical diagnosis does not yet exist and the purpose of this paper is to review where the authors now stand with regard to the construction of such a theory.
Abstract: The medical clinician has to make decisions about ( 1) management and therapeutics and (2) diagnosis. Diagnosis, that is, the classification of a particular patient, is necessitated by the need for communication among clinicians (and between clinician and patient). Reference to the literature of therapeutics and record keeping are facilitated. And, no doubt, some deep psychological need is satisfied by the construction and use of diagnostic schemata. Whatever the justification, clinicians make diagnoses, and they would like to know how to make better diagnoses. The use of computers is advocated as one way to make better (and perhaps faster) diagnoses. However, utilizing a computer requires, at the least, a formal description of the (a ) diagnostic process. I believe it is safe to say that a fully satisfying theory of medical diagnosis does not yet exist. It is the purpose of this paper to review where we now stand with regard to the construction of such a theory. The concepts employed have come from many sources. Many of these are cited in an earlier review by the author (Turner, 1965) and in the excellent papers by Ledley (1965) and Lusted (1965). The new work by Feinstein (1967) should also be consulted. In addition, the monumental monograph on cluster analysis by Sokal and Sneath (1963) contains an exhaustive review and bibliography of work on that part of our subject.
TL;DR: In this paper, a large main cluster and smaller satellite clusters within a few tens of angstroms of the main cluster are nucleated from vapor on the cleavage face of muscovite mica in ultra-high vacuum.
Abstract: Groups of gold clusters consisting of a large main cluster and smaller satellite clusters within a few tens of angstroms of the main cluster are nucleated from vapor on the cleavage face of muscovite mica in ultra-high vacuum. The satellites are seen for low cluster nucleation densities for which the random occurrence of such close cluster formations is extremely unlikely. The dependence of the average frequency of satellite occurrence per cluster upon substrate temperature and gold flux is examined. In addition, the relationship between the frequency of satellite observation and the diameters of the clusters with satellites is studied for fixed evaporation conditions. The satellites are tentatively interpreted as resulting from cluster nucleation on gold atom pairs which have escaped from established parent clusters.
01 Jan 1969
TL;DR: As an alternative to their description as vibrational levels, the low excited states of even-even nuclei can be described as rotational states of a helion, dineutron, diproton, or other cluster about the rest of the nucleus, leading to reasonable values of the average distance between centers of the clusters.
Abstract: As an alternative to their description as vibrational levels, the low excited states of even-even nuclei can be described as rotational states of a helion, dineutron, diproton, or other cluster about the rest of the nucleus, leading to reasonable values of the average distance between centers of the clusters. Some states involve rotational excitation of two or more helions or other clusters. The nature of the rotating clusters is determined by the relation of the neutron and proton numbers to the magic numbers.
TL;DR: In this paper, the Curie temperatures and asymptotic Curie temperature were calculated for mixed magnetic systems by a semi-classical Bethe-Peierls-Weiss cluster approach.
01 Feb 1969