We present an efficient numerical technique to evaluate the matrix of the (quasiparticle-) random-phase approximation, using the finite-amplitude method (FAM). The method is tested in calculation of monopole excitations in ${}^{120}$Sn, compared with result obtained with the former iterative FAM. The neutron-pair-transfer modes are calculated with the present method and their character change in neutron-rich Pb isotopes is discussed. Computational aspects of different FAM approaches are also discussed for future applications to a large-scale computation.

• Received 25 October 2012

DOI:https://doi.org/10.1103/PhysRevC.87.014331