### ASA 127th Meeting M.I.T. 1994 June 6-10

## 5aUW16. Resonance scattering theory for strongly overlapping resonances.

**D. Guicking
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H. Peine
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*Drittes Physikalisches Inst., Univ. of Gottingen, Burger-str. 42--44,
D-37073 Gottingen, Germany
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The classification of submerged bodies with respect to internal properties
(material, etc.), rather than 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 possible by applying to the acoustical scattering problem
the so-called R-matrix theory (RMT), which has been developed by Wigner and
Eisenbud to describe nuclear reactions. This theory includes in a natural way
the linewidths, the coupling of the different resonant modes, and the
overlapping of the resonances. Properly defined resonances provide the basis
from which the whole formalism is constructed, while in the former theory the
resonances are introduced after computing the scattering cross section. This
allows an extension of the ``acoustical spectroscopy'' of isolated resonances
as introduced by Brill to the practically important case of strongly
overlapping resonances. However, isolated resonances are included in the RMT
theory as special cases as well. A model function is proposed that can be
matched---without knowledge of the scattering cross section---to measured
differential cross sections in order to extract the resonance features.