No abstract

A new theory of the electronic structure of molecules is proposed, based on a wavefunction of the following type: φSCF−BI=NAψ(1,2)ψ(3,4)···ψ(2N···1,2N).This wavefunction is called the self-consistent-field biorbital wavefunction, and the factors ψ(i, j) are called biorbitals. This function is discussed, the corresponding energy expression is derived, and the variational equations leading to the best possible φSCF–BI are presented. This theory is the molecular version of Blatt's theory of superconducting systems.

The unusual features of the infrared spectra of molecules with hydrogen bonds are discussed. It is shown that the broad hydrogen stretching bands associated with strong hydrogen bonds are not single bands, but groups of bands which are very sensitive to intermolecular influences. This is due to the anharmonicity of some parts of the (effective) molecular potential energy surface. This surface occasionally has two minima which implies typical double minimum phenomena. Variations in the intensity of the hydrogen stretching bands in going from the nonbonded to the bonded molecules is discussed and an explanation attributing this variation to the charge transfer associated with the hydrogen bond formation is offered.

A theory is proposed to explain the ir spectra of inert solutions of diatomic molecules. The theory is a stochastic-type theory related to similar theories of the NMR spectra. The vapor-solution band shifts are shown to depend on the difference between the solvent–solute interaction energies of the two vibrational states involved in the transition. The band profiles are basically asymmetrical; nevertheless, symmetric limiting forms exist as well. The theory predicts the existence of a continuous sequence of band forms comprising, among others, the profile with P- and R-type wings, the Lorentzian profile, the Gaussian profile, the Voigt profile, and several sorts of asymmetric profiles. The relation between a given band form and the nature of the dominating relaxation process is discussed.

A theory is proposed to explain the ir spectra of highly compressed gas mixtures of the type HCl+X (or HBr, HF with X=He, Ar, Xe, N2, CO, etc.). This theory is based on the following three hypotheses: (1) The compressed mixture is formed of three molecular species, free HCl (or HBr, HF, etc.), free X, and bound van der Waals molecules (HCl···X). (2) In thermodynamic equilibrium, the system is subject to the law of mass action: HCl+X⇌(HCl···X). (3) The equilibrium constant is given by the standard formula K(T) = exp(—ΔF/RT). Using these hypotheses, the spectral perturbations are explained in terms of the calculated properties of the bound van der Waals molecules. The theory predicts that three limiting types of van der Waals molecules exist according to whether the energy of coupling between the rotation of HCl and the over-all rotation of the complex is (1) smaller than the energy of the over-all rotation of the complex [Coupling Case (1)], (2) larger than the energy of the over-all rotation of the complex but smaller than the energy of the rotation of HCl [Coupling Case (b)], (3) much larger than the energy of rotation of HCl [Coupling Case (c)]. The energy expressions are given for the three coupling cases, the equilibrium constants K (T) are calculated and the spectral perturbations are analyzed. In particular, the fine structure of the induced band is discussed.