Importance Of Many-body Effects Research Articles

Energy-band distortion in highly doped silicon

A plausible model for the doping dependences of the conduction-and valence-band shifts, and of the concomitant narrowings of the optical and electrical energy gaps, caused by high doping concentrations in silicon is developed by refining, extending, and combining previously described theories. A meaningful link is thereby established between the fundamental solid-state physics that underlies the energy-band distortion and the silicon device physics that describes the pragmatic ramifications of it. The important many-body effects, which produce actual rigid shifts in the conduction and valance bands, are identified and characterized, and are shown to exclusively narrow the optical energy gap. The electrical energy-gap narrowing comprises additional effective shifts defined by the band tails due to the randomness of the dopant distribution, which are described. Predictions of the optical and electrical energy-gap narrowings, the difference between which is explained physically for the first time, are shown to agree well with measurements from several independent experiments.

Optical transitions from d core states in amorphous selenium, arsenic and arsenic triselenide

Abstract Absorption measurements on amorphous selenium, arsenic and arsenic triselenide have been performed using synchrotron radiation. The results obtained reveal the importance of many body effects, matrix elements, and site of the initial state in the interpretation of optical data corresponding to transitions from core levels.

Approach to the calculation of the important many-body effects on photoabsorption oscillator strengths

By a combination of selection rules for dipole transitions and notions from variation-perturbation theory, we develop a first-order theory of oscillator strengths (FOTOS) whereby the important correlations for an accurate treatment of electric dipole processes in atoms and molecules can be easily understood, formally derived and calculated. FOTOS is applied here to certain one- and two-electron transitions in Li I, N I and N II. The calculation of the corresponding oscillator strengths present considerable theoretical problems. Our results resolve the existing discrepancy between lifetime experiments and previous many-body calculations.

Resonance Broadening of Absorption Lines

A general theory of line broadening is used to study the effects of collisions on absorption line shapes when self-broadening is important. Special attention is focused on the role of processes in which an excited atom transfers its electronic excitation to an unexcited atom; it is this process which distinguishes self-broadening from foreign-gas broadening. Several forms for the absorption rate are presented corresponding to particular assumptions about the amplitudes associated with this phenomenon. For example, one approximation leads to a generalized Lorentz-Lorenz law in which the one-atom polarizability is replaced by one that accounts for line broadening. Finally, the importance of many-body effects in the calculation of the linewidth is briefly discussed to determine when simple impact theories are applicable.