8 research outputs found
Configuration interaction in delta-doped heterostructures
We analyze the tunnel coupling between an impurity state located in a δ-layer and the 2D delocalized
states in the quantum well (QW) located at a few nanometers from the δ-layer. The problem is formulated in
terms of Anderson–Fano model as configuration interaction between the carrier bound state at the impurity
and the continuum of delocalized states in the QW. An effect of this interaction on the interband optical transitions
in the QW is analyzed. The results are discussed regarding the series of experiments on the GaAs
structures with a δ-Mn layer
Radioheliograph observations of microwave bursts with zebra structures
The so-called zebra structures in radio dynamic spectra, specifically their
frequencies and frequency drifts of emission stripes, contain information on
the plasma parameters in the coronal part of flare loops. This paper presents
observations of zebra structures in a microwave range. Dynamic spectra were
recorded by Chinese spectro-polarimeters in the frequency band close to the
working frequencies of the Siberian Solar Radio Telescope. The emission sources
are localized in the flare regions, and we are able to estimate the plasma
parameters in the generation sites using X-ray data. The interpretation of the
zebra structures in terms of the existing theories is discussed. The conclusion
has been arrived that the preferred generation mechanism of zebra structures in
the microwave range is the conversion of plasma waves to electromagnetic
emission on the double plasma resonance surfaces distributed across a flare
loop.Comment: 18 pages, 7 figure
High Spectral Resolution Observation of Decimetric Radio Spikes Emitted by Solar Flares – First Results of the Phoenix-3 Spectrometer
A new multichannel spectrometer, Phoenix-3, is in operation having
capabilities to observe solar flare radio emissions in the 0.1 - 5 GHz range at
an unprecedented spectral resolution of 61.0 kHz with high sensitivity. The
present setup for routine observations allows measuring circular polarization,
but requires a data compression to 4096 frequency channels in the 1 - 5 GHz
range and to a temporal resolution of 200 ms. First results are presented by
means of a well observed event that included narrowband spikes at 350 - 850
MHz. Spike bandwidths are found to have a power-law distribution, dropping off
below a value of 2 MHz for full width at half maximum (FWHM). The narrowest
spikes have a FWHM bandwidth less than 0.3 MHz or 0.04% of the central
frequency. The smallest half-power increase occurs within 0.104 MHz at 443.5
MHz, which is close to the predicted natural width of maser emission. The
spectrum of spikes is found to be asymmetric, having an enhanced low-frequency
tail. The distribution of the total spike flux is approximately an exponential.Comment: Solar Physics, in pres