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Physics

Air Force Institute of Technology

Series

2013

Articles 1 - 6 of 6

Full-Text Articles in Physical Sciences and Mathematics

Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton Sep 2013

Ground State Of The Singly Ionized Oxygen Vacancy In Rutile Tio2, A. T. Brant, Nancy C. Giles, Shan Yang (杨山), M. A. R. Sarker, S. Watauchi, M. Nagao, I. Tanaka, D. A. Tryk, A. Manivannan, Larry E. Halliburton

Faculty Publications

Results from electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) experiments are used to establish the model for the ground state of the singly ionized oxygen vacancy in the interior of bulk rutile TiO2 crystals. Hyperfine from 47Ti and 49Ti nuclei show that the unpaired electron in this S = 1/2 defect is localized on one titanium ion adjacent to the oxygen vacancy (i.e., the spin is not shared by two titanium ions). These defects are formed at low temperature (∼35 K) in as-grown oxidized crystals when sub-band-gap 442 nm laser light converts doubly ionized nonparamagnetic …

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Why A 15 Minute Biological Detection System?, Doug Lewis Jul 2013

Why A 15 Minute Biological Detection System?, Doug Lewis

Faculty Publications

The biological defense community needs to take a hard look at the requirements and assumptions we use to develop our biological sensors. Today the point sensors currently deployed or in development can offer at best “near real time” detection. This translates into approximately 10-20 minutes from the time an agent passes over the device until an alarm is issued. Why are we working to develop detection hardware which in reality contributes little to no advantage to an operational environment? Should the DOD resist fielding (in the near term) “near real time” detection systems, and instead field slower (but much more …

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Temperature-Dependent Photoluminescence Of Ge/Si And Ge 1-Ysn Y/Si, Indicating Possible Indirect-To-Direct Bandgap Transition At Lower Sn Content, Mee-Yi Ryu, Thomas R. Harris, Yung Kee Yeo, Richard T. Beeler, John Kouvetakis May 2013

Temperature-Dependent Photoluminescence Of Ge/Si And Ge 1-Ysn Y/Si, Indicating Possible Indirect-To-Direct Bandgap Transition At Lower Sn Content, Mee-Yi Ryu, Thomas R. Harris, Yung Kee Yeo, Richard T. Beeler, John Kouvetakis

Faculty Publications

Temperature (T)-dependent photoluminescence (PL) has been investigated for both p-Ge and n-Ge1-ySny films grown on Si substrates. For the p-Ge, strong direct bandgap (ED) along with weak indirect bandgap related (EID) PL at low temperatures (LTs) and strong ED PL at room temperature (RT) were observed. In contrast, for the n-Ge1-ySny, very strong dominant EID PL at LT and strong ED PL were observed at RT. This T-dependent PL study indicates that the indirect-to-direct bandgap transitions of Ge1-ySn …

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Reversible Mn Segregation At The Polar Surface Of Lithium Tetraborate, Christina L. Dugan, Robert L. Hengehold, Stephen R. Mchale, Juan A. Colon Santana, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Ya B. Losovyj, Peter A. Dowben Apr 2013

Reversible Mn Segregation At The Polar Surface Of Lithium Tetraborate, Christina L. Dugan, Robert L. Hengehold, Stephen R. Mchale, Juan A. Colon Santana, John W. Mcclory, Volodymyr T. Adamiv, Yaroslav V. Burak, Ya B. Losovyj, Peter A. Dowben

Faculty Publications

We find Mn surface segregation for single crystals of Mn doped Li2B4O7, nominally Li1.95Mn0.05B4O7(001), but as the temperature increases, evidence of this Mn surface segregation diminishes significantly. At room temperature, the surface photovoltaic charging is significant for this pyroelectric material but is quenched at a temperature well below that seen for the undoped Li2B4O7 samples. The suppression of surface charging in the region of 120 °C that accompanies the temperature of Mn dissolution in the bulk of Li2B4 …

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Role Of Excited State Photoionization In The 852.1 Nm Cs Laser Pumped By Cs-Ar Photoassociation, J. D. Hewitt, T. J. Houlahan Jr., Jeffrey E. Gallagher, D. L. Carroll, A. D. Palla, J. T. Verdeyen, Glen P. Perram, J. G. Eden Mar 2013

Role Of Excited State Photoionization In The 852.1 Nm Cs Laser Pumped By Cs-Ar Photoassociation, J. D. Hewitt, T. J. Houlahan Jr., Jeffrey E. Gallagher, D. L. Carroll, A. D. Palla, J. T. Verdeyen, Glen P. Perram, J. G. Eden

Faculty Publications

Photoionization of Cs (6p 2P3/2) atoms during the operation of a Cs D2 line (852.1 nm: 6p 2P3/2→6s 2S1/2) laser, pumped by free→free transitions of thermal Cs-Ar ground state pairs, has been investigated experimentally and computationally. Photoexcitation of Cs vapor/Ar mixtures through the blue satellite of the D2 transition (peaking at 836.7 nm) selectively populates the 2P3/2 upper laser level by the dissociation of the CsAr excited complex. Comparison of laser output energy data, for instantaneous pump powers up to 3 MW, with the …

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Insertion Of Lithium Ions Into Tio2 (Rutile) Crystals: An Electron Paramagnetic Resonance Study Of The Li-Associated Ti3+ Small Polaron, A. T. Brant, Nancy C. Giles, Larry E. Halliburton Feb 2013

Insertion Of Lithium Ions Into Tio2 (Rutile) Crystals: An Electron Paramagnetic Resonance Study Of The Li-Associated Ti3+ Small Polaron, A. T. Brant, Nancy C. Giles, Larry E. Halliburton

Faculty Publications

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) are used to identify a Ti3+-Li+ complex in TiO2 crystals having the rutile structure. This defect consists of an interstitial Li+ ion adjacent to a substitutional Ti3+ ion (the unpaired electron on the Ti3+ ion provides charge compensation for the Li+ ion). The neutral Ti3+-Li+ complex is best described as a donor-bound small polaron and is similar in structure to the recently reported neutral fluorine and hydrogen donors in TiO2 (rutile). Lithium ions are diffused into the crystals at …

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