In 1963, Salmeron returned to Brazil and accepted a post as professor of physics in the newly created Universidade de Brasília. Unfortunately, the military dictatorship repressed strongly the faculty with liberal and leftist ideas and he joined 223 other professors in protest, who resigned from the University in October 1965.
In 1966 Salmeron left definitely Brazil and went to work in Europe at CERN again, where he had an important role in experiments attempting to discover the quark–gluon plasma. Afterwards (1967) he worked at the École Polytechnique in Paris, France, one of the most important schools of engineering in the world.