SPS Zone 5 Home Page: Student Abstracts

Recombination and Free-Carrier Diffusion Near an Isolated Defect in GaAs
Mark Crowley (Davidson), T. Gfroerer, and M. Wanlass

When electron-hole pairs are generated in GaAs-based solar cells, they can recombine by emitting light before being extracted for electricity.  In images of optical emission from GaAs, we observe isolated dark regions where the darkened area decreases substantially with increasing laser excitation.

Exploring Free Carrier Diffusion with Light- and Heat-Generating Recombination
Ryan Crum (Davidson), T. Gfroerer, and M. Wanlass

Light- and heat-generating recombination decrease the efficiency of GaAs-based solar cells, while free carrier diffusion is an important mechanism for modeling solar cell performance.  We seek an accurate measurement of the diffusion-driven free carrier distribution in GaAs near a tightly focused laser excitation spot.    

Radioisotope-Powered Hopper Design for Europan Mission
Melissa Guzman (Davidson), et al. (Center for Space Nuclear Research)

NASA and ESA have prioritized an outer planet flagship mission to Jupiter and its four largest moons.  The Europa Hopper model utilizes a radioisotope core, in-situ materials and a subsurface ice probe in order to minimize mass and power needs.  The hopper also maximizes surface area coverage of Europa.  

Low-Resolution Photodetachment Spectroscopy of the S2- Ion
Wade Morgan (Davidson) and J. Yukich

Numerous experiments have investigated the properties and dynamics of single- atom negative ions.  Similar experiments can be conducted with molecular negative ions.  Our results yield a lower-limit estimate of the minimum detachment threshold energy.    

Photometry of Delta Scuti variables
Jason York, J. D'Arruda, and Nathan Stewart (UNCP)

Delta Scuti stars are a variable stars that exhibit an extremely short period (The prototypical star Delta Scuti is 4.65 hours) in their luminosity curves generally varying in brightness from 0.003 to 0.9 magnitude in V.  These stars are photographed and measured against comparison stars in the field.  

Applying the Planck-Einstein relation to light emitting diodes
Austin Griffin and Stuart Hanmer (UNCP)

We have investigated alternative experimental techniques to measure the quantized energy emission associated with LEDs based on the Planck-Einstein relation.  We applied the equation using a novel measurement based on the relative external efficiency of various LEDs.  

Effects of Ultrasound on Enzymatic Reaction Rates
David Blake (UNCP)

Ultrasound's prevalence in medicine, industry and agriculture has highlighted its potential as a tool.  We have developed methodology to measure changes of enzymatic reaction rates under ultrasound influence in real time, and the preliminary data is presented.  A prototype apparatus of a spectrophotometer modified with a 1.08 MHz transducer was used.  

Ytterbium and Erbium in Sol Gel Glass
Lindsey Martin (Davidson) and D. Boye

Trivalent rare earth ions, such as ytterbium and erbium, emit distinctive luminescence when their excited electrons return to the ground state.  Efficient means for directly exciting the electrons of a specific rare earth are not always available. Different rare earth species can be paired so that the excitation from one ion transfers to the other which then emits its own distinct spectrum of light.

The Biharmonic Oscillator and Asymmetric Linear Potentials in the Extreme Quantum Limit
Leah Ruckle (Davidson), M. Belloni, and R. Robinett

The biharmonic oscillator and the asymmetric linear well provide two model systems for which complete bound state solutions are possible in both classical and quantum mechanics. We examine these problems in detail, focusing on the behavior of momentum-space wave functions for large momenta.
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