Infrared transient absorption of excitons and biexcitons confined in CuCl quantum dots

We have measured the mid-infrared transient absorption of CuCl quantum dots embedded in a NaCl matrix with picosecond temporal resolution. The transient absorption exhibited two decay components that are attributable to confined excitons and biexcitons. This result indicates the existence of stable excited states of biexcitons confined in the quantum dots, although the energy separation between the ground and excited states of a biexciton is larger than its binding energy in bulk crystals.