Relaxation Process of Excitonic Molecules in CuCl under the Two-Photon Resonant Excitation. I. Mutual Collision of Excitonic Molecules

Abstract

Line shapes of the giant two-photon absorption (GTA) band for the direct generation of excitonic molecules (EM) and the subsequent secondary emission of the EM resonantly generated have been studied in CuCl at various pump powers with the use of a high resolution spectroscopic method. The mutual collision of the EM, the rate of which is nearly proportional to their density, is found to be the main origin for causing the broadening of the GTA band, the decrease of the Raman yield and the rapid increase of the EM luminescence. The collision rate increases up to 10¹²/sec for the pump power of ∼1 MW/cm². With the use of pump and probe method further evidence is obtained for the effectiveness of the mutual collision of the EM.