Quantum modeling of two-level photovoltaic systems

We present a quantum formalism that provides a quantitative picture of the fundamental processes of charge separation that follow an absorption event. We apply the formalism to two-level photovoltaic cells and our purpose is to pedagogically explain the main aspects of the model. The formalism is developed in the energy domain and provides detailed knowledge about existence or absence of localized states and their effects on electronic structure and photovoltaic yield.

On the relations between proton influx and D-region electron densities during the polar-cap absorption event of 28-29 October 2003

Observations by incoherent-scatter radar have been applied to explore relationships between the fluxes of incident protons and the resulting D-region electron densities during a polar-cap radio-absorption event. Using proton flux data from a GOES geosynchronous satellite, the energy band having the greatest influence at a selected height is estimated by a process of trial and error, and empirical relationships are defined. The height profiles of the effective recombination coefficient are determined for day and night, and the transition over the evening twilight is investigated for the height range 60-70 km. The results show that the day-night change is confined to heights below 80 km, night-time values at the lower levels being consistent with a balance between negative ions and electrons controlled by 3-body attachment and collisional detachment. The daytime results confirm that, contrary to the prediction of some chemical models, a square-law continuity equation may be strictly applied. It is confirmed that, as previously reported, the timing of the sunset change varies with altitude.

A localised co-rotating auroral absorption event observed near noon using imaging riometer and EISCAT

An isolated region of energetic electron precipitation observed near local noon in the auroral zone has been investigated using imaging riometer (IRIS) and incoherent-scatter radar (EISCAT) techniques. IRIS revealed that the absorption event was essentially co-rotating with the Earth for about 2 h. The spatial and temporal variations in D-region electron density seen by EISCAT were able to be interpreted within a proper context when compared with the IRIS data. EISCAT detected significant increases in electron density at altitudes as low as 65 km as the event drifted through the radar beam. The altitude distribution of incremental radio absorption revealed that more than half of the absorption occurred below 75 km, with a maximum of 67 km. The energy spectrum of the precipitating electrons was highly uniform throughout the event, and could be described analytically by the sum of three exponential distributions with characteristic energies of 6, 70 and 250 keV. A profile of effective recombination coefficient that resulted in self-consistent agreement between observed electron desities and those inferred from an inversion procedure has been deduced. The observations suggest a co-rotating magnetospheric source region on closed dayside field lines. However, a mechanism is required that can sustain such hard precipitation for the relatively long duration of the event.

Actinide Speciation by Photothermal Spectroscopies: Instrumentation Development

ABSTRACTPhotoacoustic spectroscopy using pulsed laser excitation is being developed by a number of research groups as one of the most promising methods for studying speciation of actinides in solution at environmentally relevant concentrations. We present details of a number of hardware and software techniques we have implemented which, once fully developed, we believe will improve the sensitivity of the method. Our approach is based on more extensive waveform analysis. While most signal processing techniques extract the analytical signal from only a small portion of the acoustic waveform produced in the detector by an absorption event, we describe two methods that use more of the waveform. Other methods of minimizing noise sources using both hardware and software are also described.