Electron-vibrational Interaction Research Articles

The anomalous variation of successive molecular ionization energies and the electron-vibrational interaction

In this work we point out the conditions which determine the anomalous variation of successive molecular ionization energies. It is shown that this variation arises when the strong electronvibrational interaction coming from the change of the number of electrons in a molecule exceeds the Coulomb electronic repulsion. The interrelation between this effect and the mechanism of the disproportionation reaction is discussed.

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A series of Mn2+ doped Ba2MgSi2O7 phosphors with a nominal formula Ba2Mg1−xMnxSi2O7 (x = 0.01–0.13) were prepared by a high-temperature solid-state reaction technique. Their VUV–vis photoluminescence spectra, fluorescence decay curves, and low-voltage cathodoluminescence spectra were measured and discussed in detail. The results confirm that the Mn2+ ions enter into the four-coordinated Mg2+ site in Ba2MgSi2O7 host lattice. The main electron-vibrational interaction (EVI) parameters (such as Huang–Rhys factor, effective phonon energy and position of the zero-phonon line) were evaluated from the experimental spectra. Furthermore, the concentration and the temperature dependence of the emission intensity and the luminescence decays of Ba2MgSi2O7:Mn2+ were investigated, accordingly the schematic energy levels for Mn2+ in Ba2MgSi2O7 were proposed. Due to the high emission intensity under low-voltage electron beam excitation, a further optimized sample Ba2Mg0.95Mn0.05Si2O7 can be considered as a promising green phosphor for field emission displays (FEDs).

On the optical properties of glasses

Intrinsic features of electron-vibrational interaction in glasses and in the ‘glass-microcrystal inclusions’ systems are considered. Changes in optical properties of glass by means of an intensive light flux is stressed. A new method to record optically information using radiative color centers is suggested. Peculiarities of the optical breakdown of glasses in a super-small spot are described. The studies of optical properties of a modified glass surface are indicated to be promising.

Optical properties of quasi-one-dimensional molecular crystals with different polarizations

Quasi-one-dimensional organic compounds in which the acceptor TCNQ molecules form dimers are studied. Site Orbitals describing the π electron in half of the TCNQ molecule are introduced. Hubbard's model is generalized so as to take into account the Coulomb repulsion between two electrons at one site. It is shown that the optical excitations of the electron are asssociated with intramolecular vibrations both when the incident light is polarized along the TCNQ chains and when the incident radiation is polarized transverse to the chains. The conductivity of the system with different polarizations is calculated taking into account the electron-vibrational interaction.

Dissociative attachment in e--HCl, DCl collisions

Dissociative attachment of electrons on the various rovibrational levels of the HCl and DCl molecules is studied in the 0-1 eV collision energy range. The interaction between the electron and the neutral molecule is described in an effective range theory which explicitly includes the long-range polarisation forces and represents the short-range forces by a boundary condition. This allows for an exact treatment of the electron-vibrational motion interaction in the course of the collision. The collision equations are solved for the associative detachment process and the dissociative attachment process is obtained through the detailed balance principle. The non-adiabatic effects are taken into account, they are responsible for the dissociative attachment process which does not imply an intermediate resonant state. The R dependence of the boundary condition is adjusted in order to reproduce the available experimental data on vibrational excitation and dissociative attachment on thermal molecules as given by Rohr and Linder (1976) and Allan and Wong (1981).

Electron-vibrational interaction in polyatomic molecules. Taking molecular symmetry into account

Electron-vibrational interaction in polyatomic molecules. Taking molecular symmetry into account

Forbidden rotational transitions in molecules

The present state of theoretical and experimental research on forbidden rotational transitions in polar and nonpolar molecules, initiated mainly in 1971, is reviewed. Three mechanisms whereby forbidden rotational transitions appear are considered: 1) centrifugal distortion, 2) anharmonicity of the potential energy, 3) electron-vibrational interaction (the Jahn-Teller effect). A method is described for calculating the effective dipole moment and the strength of a transition, based on sucessive contact transformations of the Hamiltonian and of the dipole moment operator. Formulas are given for the line strengths of the most important classes of molecules. Results are presented of experimental investigations of centrifugal transitions of tetrahedral hydride molecules by the double resonance and microwave and infrared spectroscopy methods. Particular attention is paid to Jahn-Teller transitions, which have not yet been observed. An approximate estimate is made, for the first time, of the dipole moment of such transitions in triply degenerate electronic states of molecules (such as the ground state of methane) and it is shown that the Jahn-Teller transition strengths can be of the same order as of the anharmonic and centrifugal transitions.