1. Spectroscopy
and Polymers Laboratory (LEPOL), Department of Physics, Federal University of Santa Maria, CEP 97105-900 Santa
Maria, RS, Brazil
2. Department
of Chemistry (NUQUIMHE), Federal University of Santa Maria, CEP 97105-900 Santa Maria, RS, Brazil
3. Institute
of Chemistry, Federal University of Rio Grande do Sul, CEP 91501-970 Porto Alegre, RS, Brazil