The highly structured profile of the ${\Gamma }_1$ biexciton level of CuCl is studied experimentally by resonant coherent nonlinear scattering. A theoretical model is presented which accurately describes the ${\Gamma }_1$ biexciton line shape in terms of a Fano interference, evidencing the autoionizing character of biexcitons.

• Received 2 February 1979

DOI:https://doi.org/10.1103/PhysRevLett.42.1075