Photoionization Spectra and Ionization
Potentials of Energetic Molecules
Itamar Borges Jr. and Elmar Uhl
Abstract We examine theoretically photoionization processes of molecules
component of explosives having at least one explosophore group NO 2 . We
review previous results obtained for the nitramide, N,N-dimethylnitramine and
1,1-diamino-2,2-dinitroethylene (FOX-7 or DADNE) molecules and present new
results for the two conformers of nitromethane. A systematization of the results is
given. The calculations employed the Symmetry-Adapted-Cluster Configuration
Interaction (SAC-CI) ab initio wave function and the monopole approximation to
compute photoionization cross sections. Assignments of the ionization bands are
provided. The overall agreement between computed spectra, ionization potentials
and experiment is very good. We show that the SAC-CI ionization potentials are far
superior when compared with Koopmans theorem values and much closer to
experimental values.
Keywords Photoionization Á Ionization Potential Á Energetic materials Á Koopman’s
theorem Á Excited states Á ab initio wave function Á SAC-CI
1 Introduction
Propellants and explosives composed of nitro compounds are an important class of
energetic materials. They have numerous applications and their decomposition
processes are especially important because occur at relatively low temperatures and
are involved in the detonation of explosives [14, 19]. The considerable experimental difficulties related to examining the complex chemical processes associated
with the decomposition of nitro molecules give especial relevance to theoretical
investigations in this field.
I. Borges Jr. (&) Á E. Uhl
Departamento de Química e Programa de Pós-Graduação em Engenharia de Defesa,
Instituto Militar de Engenharia, Rio de Janeiro 22290-270, Brazil
e-mail: itamar@ime.eb.br
© Springer International Publishing Switzerland 2015
M.A.C. Nascimento et al. (eds.), Frontiers in Quantum Methods and Applications
in Chemistry and Physics, Progress in Theoretical Chemistry and Physics 29,
DOI 10.1007/978-3-319-14397-2_9
147
Potentials of Energetic Molecules
Itamar Borges Jr. and Elmar Uhl
Abstract We examine theoretically photoionization processes of molecules
component of explosives having at least one explosophore group NO 2 . We
review previous results obtained for the nitramide, N,N-dimethylnitramine and
1,1-diamino-2,2-dinitroethylene (FOX-7 or DADNE) molecules and present new
results for the two conformers of nitromethane. A systematization of the results is
given. The calculations employed the Symmetry-Adapted-Cluster Configuration
Interaction (SAC-CI) ab initio wave function and the monopole approximation to
compute photoionization cross sections. Assignments of the ionization bands are
provided. The overall agreement between computed spectra, ionization potentials
and experiment is very good. We show that the SAC-CI ionization potentials are far
superior when compared with Koopmans theorem values and much closer to
experimental values.
Keywords Photoionization Á Ionization Potential Á Energetic materials Á Koopman’s
theorem Á Excited states Á ab initio wave function Á SAC-CI
1 Introduction
Propellants and explosives composed of nitro compounds are an important class of
energetic materials. They have numerous applications and their decomposition
processes are especially important because occur at relatively low temperatures and
are involved in the detonation of explosives [14, 19]. The considerable experimental difficulties related to examining the complex chemical processes associated
with the decomposition of nitro molecules give especial relevance to theoretical
investigations in this field.
I. Borges Jr. (&) Á E. Uhl
Departamento de Química e Programa de Pós-Graduação em Engenharia de Defesa,
Instituto Militar de Engenharia, Rio de Janeiro 22290-270, Brazil
e-mail: itamar@ime.eb.br
© Springer International Publishing Switzerland 2015
M.A.C. Nascimento et al. (eds.), Frontiers in Quantum Methods and Applications
in Chemistry and Physics, Progress in Theoretical Chemistry and Physics 29,
DOI 10.1007/978-3-319-14397-2_9
147