Canonical form of transition matrix elements

The calculation of complicated transition matrix elements between multiquasiparticle states can be essentially simplified by transforming them in a canonical form. This method allows the extension of the basis space of generator coordinate studies aiming to include orthogonal quasiparticle excitations into the commonly considered basis set of collective states. Furthermore, it is shown that the neglect of the exchange contribution of multipole forces may lead to dangerous pole terms in nondiagonal matrix elements.