The α-α correlation at small relative angles has been measured for ４０Ar-induced reactions on 197Au at E/A=25MeV, in coincidence with two fission fragments. The relative populations of states of 8Be and emission temperature of hot nuclei are extracted from the α-α correlation function. The emission temperature changes slightly with the impact parameter, from about 4MeV for central collision to about 3.8MeV for peripheral collision. At peripheral collision, the emission temperature is observed to increase with the energy of particles.