  The absorption of large bipolarons is investigated using the path-integral
method. The response of a bipolaron to an external electromagnetic field is
derived in the framework of the memory-function approach. The bipolaron optical
absorption spectrum consists of a series of relatively narrow peaks. The
peculiarities of the bipolaron optical absorption as a function of the
frequency of the electromagnetic field may be attributed to the transitions
involving relaxed excited states and scattering states of a bipolaron.
