[1] Univ Fed Fluminense, Inst Fis, BR-24210900 Niteroi, RJ, Brazil
[2] Univ Estadual Campinas UNICAMP, Fac Tecnol, BR-13484332 Sao Paulo, Brazil
[3] CTA, Inst Tecnol Aeronaut, Dept Fis, BR-12228900 Sao Jose Dos Campos, Brazil
[4] UNESP Univ Estadual Paulista, Inst Fis Teor, BR-01140070 Sao Paulo, Brazil