Pressure Broadening of Some He I Lines

Quantum statistical approach is adopted for calculating the spectral line shapes of neutral helium in dense plasmas. Stark broadening of isolated He I lines 5048 Å (), 3889 Å (), and 3188Å () is presented. Based on thermodynamic Green's function, the electronic contribution to the shift and width is considered. The participation of ions to the line broadening is treated in a quasistatic approximation, by taking both quadratic Stark effect and quadrupole interaction into account. The calculated shifts and widths are compared with existing data.

Engineering of Dislocation-Loops for Light Emission from Silicon Diodes

Luminescence properties of silicon light emitting diodes with engineered dislocation loops were investigated. Dislocation loops were formed by Si+-ion implantation above and below metallurgical p+-n junction followed by an annealing step. The diodes showed characteristic dislocation (D-band) and band-to-band luminescence. Measurements of carrier-injection level dependence of the D-band signal intensity were performed. The results are in agreement with the model for dislocation luminescence, which suggests rediative transition between two, dislocation-related shallow levels. A gradual blue-shift of the D-band peak positions was observed with an increase in the carrier injection level in electroluminescence and photoluminescence. A supposition about existence of strong Stark effect for the excitonic dislocation states allows explaining the observations. Namely, in the build-in electric field of the p-n junction the exciton energies are red-shifted. The injected charge carriers lower the field and thus cause the blue-shift of the peak positions. A fitting of the data using the quadratic Stark effect equation suggests 795 meV for the spectral position of D1 peak at 300 K and 0.0186 meV/(kV/cm)2 for the characteristic constant.

Profiles of Pressure Broadened Spectral Lines in an Arc Plasma

Spectral analysis of the alkali metals is characterized by pressure profiles. In the present work an electric arc has been used to calibrate the half-width of the intensity used in the construction of the ArI natural line at 4300 Å with a trace of evaporated rubidium at pressures of 1, 2 and 3 atmospheres. The results agree well with those obtained by Kusch’s line absorption equation in an electric furnace in the point of view of impact approximation, showing that the widths of the lines have Lorentz shapes. It is found that a simple treatment can be given using the quasi-static approximation of pressure broadening developed by Unsöld. The agreement of the results is good only if the shifts are large. The study shows that the pressure line profile is made up of a sum of dispersion profiles and asymmetric terms which arise from interactions of quadratic Stark effect, commonly assumed to be the force in causing foreign gas broadening