Estudo teórico dos estados eletrônicos e mecanismos fotodissociativos das moléculas SBr, SBr- e HSBr
Data
2022-06-23
Autores
Ferreira, Jéssica Jaqueline 
Orientadores
Hermoso, Willian
Tipo
Trabalho de conclusão de curso
Título da Revista
ISSN da Revista
Título de Volume
Resumo
As preocupações ambientais relacionadas à destruição do ozônio na estratosfera estão focadas no aumento da velocidade da destruição da camada de ozônio por espécies químicas que atuam como catalisadores, potencializando tal reação, tais como compostos de nitrogênio, cloro, flúor, enxofre e bromo. Este trabalho teve como foco o estudo dos sistemas contendo enxofre, bromo e hidrogênio como espécies potencialmente importantes nos ciclos catalíticos da destruição do ozônio; na literatura há indícios que estas moléculas podem estar presentes na atmosfera terrestre, porém há poucos estudos que abordem o assunto e atuação delas na destruição da camada de ozônio. Como há poucos trabalhos publicados específicos sobre os sistemas diatômicos e triatômicos, este trabalho tem sua motivação em estudar as transições eletrônicas que tenham maior probabilidade de participar de mecanismos de dissociação das espécies moleculares HSBr, SBr e SBr - , e que possam apresentar o caminho de formação de radicais na atmosfera. Sendo assim, para a molécula SBr foi realizada a descrição eletrônica, a estimativa de seção de choque parcial, cálculo de coeficientes de tunelamento e foram estudadas as transições entre o estado fundamental dubleto de simetria para os estados excitados dubletos não ligados de representações de simetrias Σ + , Σ - e Δ, respectivamente; para a molécula triatômica, HSBr, foi realizada a descrição dos aspectos energéticos e estruturais, obtivemos as propriedades espectroscópicas assim como as curvas associadas com os cortes na superfície na dissociação e determinamos o espectro de fotodissociação desta molécula e, por fim, para o ânion
diatômico SBr - obtivemos as curvas de energia potencial para os estados singletos mais baixos do estado de simetria espacial Σ + , Σ - Π e ∆, assim como um conjunto de constantes espectroscópicas dos estados ligados, uma descrição das funções de potencial e o perfil energético dos estados eletrônicos juntamente com os canais de dissociação.
Environmental concerns related to the destruction of ozone in the stratosphere are focused on increasing the rate of destruction of the ozone layer, by chemical species that act as catalysts potentiating this reaction, such as nitrogen, chlorine, fluorine, sulfur and bromine compounds. This work focused on the study of systems containing sulfur, bromine and hydrogen as potentially important species in the catalytic cycles of ozone depletion; in the literature there are indications that these molecules may be present in the Earth's atmosphere, but there are few studies that address the subject and their role in the destruction of the ozone layer. As there are few specific published works on diatomic and triatomic systems, this work is motivated to study the electronic transitions that are more likely to participate in the dissociation mechanisms of the molecular species HSBr, SBr and SBr- , and that may present the pathway of formation of radicals in the atmosphere. Therefore, for the SBr molecule, the electronic description was performed, the partial cross section estimation, tunneling coefficients were calculated and the transitions between the symmetry doublet ground state to the unbound doublet excited states of symmetry representations were studied. + , Σ- and Δ, respectively; for the triatomic molecule, HSBr, the energetic and structural aspects were described, we obtained the spectroscopic properties as well as the curves associated with the cuts on the surface in the dissociation and we determined the photodissociation spectrum of this molecule and, finally, for the diatomic anion SBr- we obtained the potential energy curves for the lowest singlet states of the spatial symmetry state Σ+, Σ- Π and Δ, as well as a set of spectroscopic constants of the bound states, a description of the potential functions and the energy profile of the electronic states along with dissociation channels.
Environmental concerns related to the destruction of ozone in the stratosphere are focused on increasing the rate of destruction of the ozone layer, by chemical species that act as catalysts potentiating this reaction, such as nitrogen, chlorine, fluorine, sulfur and bromine compounds. This work focused on the study of systems containing sulfur, bromine and hydrogen as potentially important species in the catalytic cycles of ozone depletion; in the literature there are indications that these molecules may be present in the Earth's atmosphere, but there are few studies that address the subject and their role in the destruction of the ozone layer. As there are few specific published works on diatomic and triatomic systems, this work is motivated to study the electronic transitions that are more likely to participate in the dissociation mechanisms of the molecular species HSBr, SBr and SBr- , and that may present the pathway of formation of radicals in the atmosphere. Therefore, for the SBr molecule, the electronic description was performed, the partial cross section estimation, tunneling coefficients were calculated and the transitions between the symmetry doublet ground state to the unbound doublet excited states of symmetry representations were studied. + , Σ- and Δ, respectively; for the triatomic molecule, HSBr, the energetic and structural aspects were described, we obtained the spectroscopic properties as well as the curves associated with the cuts on the surface in the dissociation and we determined the photodissociation spectrum of this molecule and, finally, for the diatomic anion SBr- we obtained the potential energy curves for the lowest singlet states of the spatial symmetry state Σ+, Σ- Π and Δ, as well as a set of spectroscopic constants of the bound states, a description of the potential functions and the energy profile of the electronic states along with dissociation channels.