Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session H4: SO-2: Spectroscopy 2 |
Hide Abstracts |
Chair: Joel Carney, NSWC - Indian Head Room: Hermitage D |
Tuesday, June 30, 2009 9:00AM - 9:15AM |
H4.00001: Time-dependent temperature measurements of expansion products from shock compressed Composition B Lalit Chhabildas, William Reinhart, Tom Thornhill Results from spectral radiance measurements using optical multi- channel analyzer over the visible and near infrared regime provide estimates of temperature from expansion products resulting from shocked Composition-B. The basic assumption made to deduce these temperature estimates is that the debris cloud is radiating as a black body with an emissivity of 1 and is independent of the wavelength. We are also assuming that the entire debris cloud is at a single temperature and there is no spatial temperature gradient. Results for Comp-B provide the time-dependent temperature expansion history over the stress regime of 28 to 130 GPa. These are the first measurements of temperature obtained from expansion products from materials shocked to very high pressures and these results will be discussed in detail. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE\_AC04-94AL85000. [Preview Abstract] |
Tuesday, June 30, 2009 9:15AM - 9:30AM |
H4.00002: Nanosecond Time Resolved and Steady State Infrared Studies of Photoinduced Decomposition of TATB at Ambient and Elevated Pressures Elizabeth A. Glascoe, Joseph M. Zaug, Michael R. Armstrong, Jonathan C. Crowhurst, Christian D. Grant, Laurence E. Fried The timescale and/or products of photo-induced decomposition of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were investigated at ambient and elevated pressures. Ultrafast time-resolved infrared and steady state Fourier transform IR (FTIR) spectroscopies were used to probe TATB and its products after photoexcitation with a 5 nanosecond pulse of 532 nm light. At ambient pressure, transient spectra of TATB indicate that the molecule has significantly decomposed within 60 nanoseconds; transient spectra also indicate that formation of CO$_{2}$, an observed decomposition product, is complete within 30-40 microseconds. Comparison of steady-state FTIR spectra obtained at ambient and elevated pressure (ca. 8 GPa) indicate that the decomposition products vary with pressure and only the high pressure decomposition produces water. [Preview Abstract] |
Tuesday, June 30, 2009 9:30AM - 10:00AM |
H4.00003: Physical and Chemical Changes in Liquid Benzene Multiply Shock Compressed to 25 GPa Invited Speaker: The dynamic, high-pressure response of liquid benzene was examined using multiple-shock compression to peak pressures from 0.6 GPa to 25 GPa. The lower temperatures generated in multiple-shock compression experiments allowed for exploration of the benzene phase diagram in regions inaccessible to single-shock experiments. Time-resolved transmission spectroscopy, Raman spectroscopy, and imaging measurements were used to monitor physical and chemical changes on sub-microsecond time scales. The transmission and imaging measurements showed no changes in the benzene transparency to 13 GPa. Up to 20 GPa the Raman spectra showed pressure-induced shifting and broadening, but no changes that could be attributed to a physical or chemical change. These results show that benzene remains in the liquid state on the experimental time scales. At 24.5 GPa, the Raman modes become indistinguishable from an increasing background within 40 ns of the sample attaining peak pressure, indicating a chemical change. A thermodynamically consistent equation of state (EOS) was constructed to calculate changes in the benzene density, temperature, and energy. Using the thermodynamic data and an idealized molecular configuration model, intermolecular separations between benzene molecules was determined. These calculations show that at 24.5 GPa, sufficient energy and $\pi$-orbital overlap exists for intermolecular bonding. The Raman data, along with the thermodynamic and intermolecular separation calculations, suggests that liquid benzene rapidly polymerizes through cycloaddition reactions when multiply-shock compressed to 24.5 GPa. [Preview Abstract] |
Tuesday, June 30, 2009 10:00AM - 10:15AM |
H4.00004: Time-resolved Raman spectroscopy of diamond crystals shocked to 60 GPa and above J.M. Lang, Y.M. Gupta Changes in the diamond Raman spectrum were measured under shock wave induced uniaxial strain. Time-resolved spectroscopy was used to observe the splitting of the triply degenerate 1332.5~cm$^{-1}$ Raman line for crystals shocked along [100] and [110] crystallographic orientations. Both natural and synthetic diamond samples were shocked to longitudinal stresses ranging from 20~GPa to 60~GPa. A spectrometer calibration error in the literature data (to 45 GPa) was discovered and corrected. After the calibration correction, the literature data and the present results are in good agreement. At 60~GPa, the Raman spectrum showed a decrease in the signal to noise ratio. Further experiments are planned to measure the splitting at stresses approaching and beyond the diamond HEL. Work supported by the DOE. [Preview Abstract] |
Tuesday, June 30, 2009 10:15AM - 10:30AM |
H4.00005: Band structure studies of buried materials using picosecond photoacoustic waves Ying Xu, Andrew Steigerwald, Jingbo Qi, Norman Tolk Time-resolved, wavelength dependent, pump probe studies using photo-generated picosecond coherent acoustic phonon (CAP) waves could provide layer-by-layer information about the electronic structure of materials over a wide depth range. At the anomaly in the electronic structures, such as the semiconductor band gap, a strong variation in the measured probe signal is observed Semiconducting heterostructures interfaces and defect distributions have been investigated and successfully characterized using the CAP technique. Two parameters are investigated in details here, the phase and the amplitude. We observe a distinctive phase discontinuity at the interfaces separating the heterostructures layers. For a radiation-damaged lattice, we show that continuously varying amplitude changes in the phonon oscillations corresponds to the variation in the electronic structure. This work confirms that CAP is a novel and effective tool to study the detailed band edge structures of materials and to characterize buried layers, with nanometer resolution. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700