The number h of papers with at least h citations has been proposed to evaluate individuals scientific research production. This index is robust in several ways but yet strongly dependent on the research field. We propose a complementary index h_I = h²/N_a^(T), with N_a^(T) Na being the total number of authors in the considered h papers. A researcher with index h_I has h_I papers with at least h_I citation if he/she had published alone. We have obtained the rank plots of h and h_I for four Brazilian scientific communities. In contrast with the h-index, the h_I index rank plots collapse into a single curve allowing comparison among different research areas.