Probing of Fast Chemical Dynamics at High Pressures and Temperatures using Pulsed Laser Techniques
Abstract
We report on our progress in developing new techniques and experiments for studies of fast chemical transformations in energetic materials under conditions of high pressure and temperature. We have developed a new ultrafast mid-to-near infrared (IR) system equipped with modulated and/or continuous wave laser heating, and completed an absorption system for measuring in situ materials at high pressures and temperatures. The systems utilize ultrafast pulse amplifying instrument (Coherent Legend Elite) in combination with an optical parametric amplifier (OPA) for generation of a range of short-pulsed frequencies used to study the dynamics of chemical systems, as well as the newly purchased pulsed broadbrand source (Leukos Pegasus). Experimental progress has excelled in the study of high-energy density materials (HEDMs), with promising results coming from the nitrogen-hydrogen mixtures. Results conclude that at high pressures (greater than 47 GPa) a nitrogen backbone structure is formed and stabilized by surrounding hydrogen atoms, in deep contrast to compressed pure nitrogen at these pressures. Moreover, we show through the use of photon or multi-photon absorption that we can generate similar compounds at significantly lower pressures (approximately 10 GPa). The metastability of these compounds was found to be fairly large, some even recoverable at ambient pressures and colder temperatures. To enhance our understanding of N2:H2 systems, alterations in the ratio of nitrogen to hydrogen mixture have been studied, specifically on high-hydrogen mixtures. In addition to HEDMs we have also studied noble gases under extreme conditions using combined compression and short-duration laser heating to study the evolution and dynamics of planets and stars.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 17, 2014
- Accession Number
- ADA623356
Entities
People
- Alex F. Goncharov
- M. F. Mahmood
- Nicholas Holtgrewe
- R. S. Mcwilliams
Organizations
- Howard University