Estudo fotodinâmicos por espectroscopia laser e radiação síncrotron: de pequenos hidrocarbonetos aos polímeros

Abstract

We present in this thesis new results on two strands of work. The first, the spectroscopy of highly excited states (Rydberg states) of HC3N (between 76000 and 90000 cm-1). This new study of Rydberg states of the HC3N spectroscopy REMPI, (3+1) photons, completes the overview of these Rydberg states, proposed by Connors et al, contributing with corrections and additions to this old analysis on absorption spectra. Our results indicate that the series most intense are of type (n +1)s and nd for the energy range studied. We assign the R' series as nds,p series, previously considered as a series np. We also assign new series, weaker, visible in the absorption spectrum and the REMPI spectrum, the ndd 1 states. Through the similarity between the structures of the super complex 3d-4s between the molecules of acetylene and HC3N we discuss a possible location for one of the p electrons on the C≡C bond, this electrons are responsible for the structure of Rydberg states in the molecule HC3N. Values are also present for the quantum defects associated with the observed states. The second, measurements of absolute photoionization cross section, with results on: the methyl radical (CH3), the atomic iodine (2P3/2) and iodomethane or methyl iodide (CH3I). To achieve this, the combination of experiments based on synchrotron radiation and VUV laser with the use of pyrolysis to the molecular break. This procedure is presented as well as respective results: the cross section of photoionization of absolute methyl radical CH3 between its ionization threshold (9.839 eV) and 11.5 eV, the first optical measurements of cross-section of absolute photoionization of iodomethane or methyl iodide, [CH3I to 118.2 nm (= 48.2 ± 7.9) Mb] and finally the cross section of photoionization of atomic iodine (I 2P3/2) between 10.4 and 11.8 eV, calibrated in absolute scale for the first time. The curves of the methyl radical (CH3)and atomic iodine were put on absolute scale, using values obtained by 118.2 nm laser measurements, [sigma]i^CH 3=6,7^2,7−1,7 and [sigma]^iI 2P3/2=74^33−23 Mb, respectively.