ACOUSTICAL RESONANCE SCATTERING-THEORY FOR STRONGLY OVERLAPPING RESONANCES

The classification of submerged bodies with respect to internal proper ties (material etc.), and not only based on geometrical shape, should be possible by means of their scattering resonances. This approach is known as the Resonance Scattering Theory (RST). An essential extension of the RST theory with respect to solving practical problems is possi ble by applying to the acoustical scattering problem the so-called R-M atrix Theory (RMT) which has been developed by Wigner and Eisenbud to describe nuclear reactions. This theory includes the line widths, the coupling of the different resonant modes, and the overlapping of the r esonances. Properly defined resonances provide the basis from which th e whole formalism is constructed, while in the former theory the reson ances are introduced after computing the scattering cross section. Thi s allows an extension of the ''acoustic spectroscopy'' of isolated res onances as introduced by Brill et al. to the practically important cas e of strongly overlapping resonances. Isolated resonances are included in the RMT theory as special cases, too. A model function is proposed which can be matched - without knowledge of the scattering cross sect ion - to measured differential cross sections in order to extract the resonance features.