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Site-Specific Photodecomposition in Conjugated Energetic Materials

Journal Article · · Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
 [1];  [2];  [2];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); North Dakota State Univ., Fargo, ND (United States). Dept. of Chemistry and Biochemistry
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
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Nonadiabatic excited-state molecular dynamics (NEXMD) has been used to study photodecomposition in a class of recently synthesized bicyclic conjugated energetic materials (CEMs) composed of fused tetrazole and tetrazine derivatives with increasing oxygen substitutions. Modification by oxygen functionalization has already been demonstrated to increase the two-photon absorption intensity in the target CEMs while simultaneously improving oxygen balance. Photodecomposition mechanisms in materials that undergo nonlinear absorption could be used to achieve controlled, direct optical initiation. For this study, we use NEXMD simulations to model the nonradiative relaxation and photodecomposition in CEMs following photoexcitation by a simulated Nd:YAG laser pulse. Excess electronic energy is quickly converted into vibrational energy on a sub-100 fs time scale resulting in bond dissociation. We find that, for the studied tetrazine derivatives, the bicyclic framework is an important structural feature that enhances the photochemical quantum yield and the high atomic oxygen content increases the relaxation lifetime and opens additional photodissociation pathways targeting the oxygen-substituted sites. The presented analysis scheme based on bond orders in the swarm of NEXMD trajectories is a useful tool for determining photochemical reactions.
Research Organization:
Los Alamos National Laboratory (LANL)
Sponsoring Organization:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Grant/Contract Number:
AC52-06NA25396
OSTI ID:
1461403
Report Number(s):
LA-UR-18-24161
Journal Information:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 29 Vol. 122; ISSN 1089-5639
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

Figures / Tables (6)

Figure 1.(p. 3)figure Figure 1.
Figure 2.(p. 4)figure Figure 2.
Scheme 1.(p. 4)figure Scheme 1.
Figure 3.(p. 5)figure Figure 3.
Table 1.(p. 5)table Table 1.
Figure 4.(p. 6)figure Figure 4.

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Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY