Armelle Denis

Reduction into a rational fraction of a thermodynamic property of the liquid state: Experimental determinations in the case of CO2 and n‐butane. Extension to the other properties

The expansivity of liquid CO2 and of n‐butane is determined as a function of pressure up to 4 kbar, from the melting temperatures up to the critical temperatures. The experimental method is piezothermal. The set of data is processed through a fit with a multipoint Pade approximant using an algorithm due to Werner. This particular technique determines, in its reduced form, the unique rational function relevant to the problem. The expansivity of the whole liquid phase is described in terms of a simple equation with four coefficients which enables calculation of the other thermodynamic properties. The general aspect of the phenomenological equations is discussed in this instance, underlining the particular behavior of the heat capacity as a function of pressure.

Double perturbation calculations of spin-spin coupling constants using localized orbitals

The Fermi contact contribution to N.M.R. spin-spin coupling constants has been calculated to the fourth order by a double perturbation development starting from a fully localized determinant, according to the assumptions of the PCILO-CNDO method. The use of diagrammatic techniques greatly simplifies the evaluation. There is a cancellation of certain types of diagram. The coupling constant between bonded atoms appears in the second order through a contribution which only depends on the appropriate bond orbital. The next orders involve the other bonds and correlation effects. For nonbonded atoms, the first contribution appears in the fourth order and results from direct delocalization through space, involving only the bonds on the two atoms. An analytical and numerical comparison with previous calculations is performed for H-H and C-H coupling constants on small organic molecules. The relative importance of the various processes is discussed for the J HH vicinal coupling constants of ethylene.

Correlation Effects on ππ* Transition Energies in the Series of Linear Polyenes. III Dynamical Correlation Effects

An optimization of the 2pz atomic orbitals is rederived for the ground‐state energy of conjugated systems. Within some reasonable assumptions, this optimization (analogous to that proposed by Silverstone and Joy) allows the orthogonalized 3pz atomic orbitals to be considered as v rtual orbitals in the CI calculation when one starts from a SCF calculation performed in the minimal basis set of optimized n = 2 atomic orbitals. The reorganization of the π* MO in the ππ* excited state leads to a spatial expansion in the singlet state and a spatial contraction in the triplet state. But this effect is less and less important when the dimension n of the π system increases, and the corresponding energetic correction decreases as n−2. A less pronounced effect is obtained on the π singly occupied orbital; the doubly occupied MOs are not significantly modified in the singlet state. The role of the 3pz atomic orbitals in the correlation effects on the transition energies is much more important. It is not mainly due t...

Linear response of stochastic multiperiodic systems in stationary states with application to stochastic electrodynamics

The general purpose of this paper is to develop a linear response formalism for stochastic multiperiodic systems; these systems being obtained by letting some stochastic perturbation act on deterministic multiperiodic systems. Such a formalism is then applied to the absorption coefficient of the harmonic oscillator, the rigid rotator and to the hydrogen atom, these systems being treated in the framework of the Stochastic Electrodynamics (SED) theory. A computer calculation was performed in order to investigate the possible behaviour of the absorption coefficient for the case of the hydrogen atom (Coulomb potential). The results are completely at variance with respect to those of Quantum Theory, and show that SED in its present state cannot provide a reasonably general model for microphysics, even from the qualitative point of view.