Banca de DEFESA: LEONARDO CERQUEIRA RIBEIRO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : LEONARDO CERQUEIRA RIBEIRO
DATE: 15/09/2023
TIME: 08:00
LOCAL: Plataforma remota RNP
TITLE:

Interaction of Photons and Electrons with Heterocyclic Organic Molecules: determination of mass spectra and absorption and ionization cross sections.

KEY WORDS:

Pyridine; Pyrrole; Time-of-flight spectra; Photoionization CrossSection; Electron Scattering; Total and Partial Cross Section; BEB.

PAGES: 158
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In order to understand the processes that occur in interstellar environments, the
mechanisms of interaction between electromagnetic radiation in the vacuum ultraviolet

(VUV) range and X-rays, and/or the impact of electrons and charged particles with polya-
tomic molecules in gaseous or ice phase. Some of these molecules are heterocyclic organic

compounds, which have in their closed chain at least one atom other than C and H, and,
according to astrobiology, may have been important for the origin of life on Earth. In this
context, this thesis developed the experimental and theoretical study on the production
rates of the molecules Pyridine (C5H5N) and Pyrrole (C4H5N) as a function of the energy
of the interacting beam, through partial photoionization and ionization cross sections that
have little or no information in the literature. Pyridine photoionization measurements were
carried out on the D05A-TGM beamline at the National Synchrotron Light Laboratory, in

Campinas-SP, in the VUV range from the ionization threshold to 21.5 eV. Thus, the frag-
mentation pattern was investigated as a function of photon energy, using a time-of-flight

mass spectrometer (TOF-MS) using the technique of coincidence between an electron and
an ion (photoelectron-photoion coincidence). Therefore, the mass spectra and the relative
ionic yield (RIY) were determined, that is, the partial production of ions, to then determine

the partial photoionization cross section (PPCSs) of Pyridine that are presented in this rese-
arch. The SCPs were obtained from the product of the RIY with the photoionization cross

sections (σi), which in turn are derived from the measurements of the photoabsorption
cross sections and the photoionization quantum efficiency obtained by our research group
through a double ionization chamber installed in the experimental chamber of the TGM
line. Regarding the measurements of the impact of electrons with energies between 10 eV
and 1 keV, these were carried out with Pyridine and Pyrrole molecules from a TOF-MS of
the Laboratory of Electronic and Photonic Collisions (LCEF) of the Chemistry Department
of the University Federal University of São Carlos (UFSCar), in São Carlos-SP. From these
measurements, the relative areas of the peaks representing the respective ionic fragments
were determined. Total ionization cross sections (TICS) were determined using the Binary
Encounter Bethe (BEB) method, using Density Functional Theory (DFT) for the basis set
aug-cc-pVTZ. Finally, through the product of the SCTI with the relative areas, the partial
ionization cross sections (PICS) of these molecules were determined and comparisons were
made with experimental and theoretical data available in the literature.

COMMITTEE MEMBERS:
Externo à Instituição - ANTÔNIO CARLOS FONTES DOS SANTOS - UFRJ
Externa à Instituição - WANIA WOLFF - UFRJ
Externa à Instituição - ANA LUCIA FERREIRA DE BARROS - CEFET/RJ
Interno - 1194645 - FREDERICO VASCONCELOS PRUDENTE
Interno - 2422135 - RICARDO DOS REIS TEIXEIRA MARINHO