Ultrafast dissociation dynamics in the radical cations of nitrotoluenes
Abstract
Understanding the initial dissociation mechanisms of isolated energetic molecules is important for developing novel energetic molecules that possess tailored properties such as high energy density and the ability to detonate upon photoinitiation. Initial bond cleavage events in energetic molecules can proceed from their electronically excited states and molecular ions via non-radiative relaxation through conical intersections on excited state potential energy surfaces on the ultrafast timescale of femtoseconds - picoseconds. The proposed work will investigate these processes in the radical cations of model energetic molecules through femtosecond time-resolved pump-probe measurements and complementary theoretical calculations. In order to understand the role of molecular structure in determining dissociation dynamics through specific pathways, a series of experiments will be performed on the three isomers of nitrotoluene, which represent structurally varied model systems for nitroaromatic energetic molecules. These volatile compounds will be directly introduced into the extraction region of a linear time-of-flight mass spectrometer, where a pair of time-delayed femtosecond laser pulses will ionize the molecule and probe the subsequent dynamics of the radical cations. The observed dynamics will be interpreted by calculating the relevant potential energy surfaces of neutral excited states and molecular ions with the density functional theory (DFT), time-dependent DFT (TDDFT), and equation-of-motion coupled cluster singles and doubles (EOMCCSD) approaches, as well as the locations of conical intersections with the complete active space self-consistent field (CASSCF) method. It is expected that the proposed time-resolved experiments will reveal novel ultrafast dissociation dynamics in the nitrotoluenes, which may also operate in nitroaromatic energetic molecules.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810051
Entities
People
- Katharine Moore Tibbetts
Organizations
- Army Contracting Command
- United States Army
- Virginia Commonwealth University