Electron transfer by singlet excited state of porphyn and electron acceptor affinity in rigid medium: photoacoustic phase angle analysis

Photoacoustic spectroscopy provides information about both amplitude and phase of the response of a system to an optical excitation process. This paper presents the studies of the phase in the electron transfer process between octaethylporphyn (OEP) and quinone molecules dispersed in a polymeric matrix. It was observed a tendency in the phase behavior to small values only in the spectral region near to 620 nm, while for shorter wavelength did not show any tendency. These measurements suggested that the electron transfer to acceptor occurred with the participation of octaethylporphyn singlet excited state.

Aplicação de metodologias FTIR de transmissão e fotoacústica à caracterização de materiais altamente energéticos: parte II

Materials obtained during the synthesis of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) were characterized by Fourier transform infrared (FTIR) transmission spectroscopy and/or Fourier transform infrared photoacoustic spectroscopy (FTIR-PAS). By these techniques the spectrometric alterations that occurred during the process were observed. The characterized species during the synthesis of HMX were alpha-HMX, beta-HMX, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and HMX/RDX mixtures. The FTIR-PAS was verified to be a promising technique of great usefulness of the characterization of highly energetic materials because it is fast, simple and requires no sample preparation unlike Fourier transform infrared transmission technique (KBr pellet). The FTIR-PAS analysis showed that with small sample quantity is possible to distinguish between thealpha-HMX and beta-HMX and to detect even in a qualitative way different HMX / RDX ratios.