Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “VIBRATIONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Spatially Offset Femtosecond Stimulated Raman Spectroscopy: Observing Exciton Transport through a Vibrational Lens

To design better molecular electronic devices, we need a strong understanding of how charges or excitons propagate, as many efficiency losses arise during transport. Exciton transport has been difficult to study because excitons tend to be short-lived, have short diffusion lengths, and can easily recombine. Here, we debut spatially offset femtosecond stimulated Raman spectroscopy (SO-FSRS), a three-pulse ultrafast microscopy technique. By offsetting the photoexcitation beam, we can monitor Raman spectral changes as a function of both time and position. We used SO-FSRS on 6,13-bis(triisopropylsilylethynyl) pentacene, a well-studied organic semiconductor used in photovoltaics and field-effect transistors. Furthermore, we demonstrated that the fast exciton and free charge carrier transport axes are identical and observed that exciton transport is less anisotropic by a factor of ~3. SO-FSRS is the first technique that directly tracks molecular structural evolution during exciton transport, which can provide roadmaps for tailor-making molecules for specific electronic devices.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Chaotic vibrations of the duffing system with fractional damping

We examined the Duffing system with a fractional damping term. Calculating the basins of attraction, we demonstrate a broad spectrum of non-linear behaviour connected with sensitivity to the initial conditions and chaos. To quantify dynamical response of the system, we propose the statistical 0-1 test as well as the maximal Lyapunov exponent; the application of the latter encounter a few difficulties because of the memory effect due to the fractional derivative. The results are confirmed by bifurcation diagrams, phase portraits, and Poincaré sections.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Structural, vibrational, and electronic properties of BaReH 9 under pressure

Here we present a study of the high-pressure behavior of BaReH 9 , a novel hydrogen-rich compound, using optical, Raman, and infrared spectroscopy as well as synchrotron x-ray diffraction. The x-ray diffraction measurements demonstrate that BaReH9 retains its hexagonal structure on room temperature compression up to 40 GPa. Optical absorption shows the absence of a gap closure to 80 GPa. Raman and IR spectra reveal the pressure evolution of a newly observed phonon peak, and large peak broadening with increasing pressure. Lastly, these data constrain the disorder present in the material following the P-T paths explored.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗