Mechanism of three-cluster fragmentation of light nuclei A(. gamma. , b/sub 1/d/sub 2/)(A--b) by 60--100 MeV photons

A practical scheme for use of the technique of fractional-parentage coefficients for separation of the wave function of the nucleus into three fragments in arbitrary internal states is described. In the example of the /sup 7/Li (..gamma.., t)/sup 4/He process the influence of the oscillations of the wave function Psi(R/sub ..cap alpha..//sub t/) on the width and position of the maximum of the cross section for two-cluster photodisintegration is demonstrated. A detailed analysis of the A(..gamma.., b/sub 1/b/sub 2/)(A--b) processes is performed in order to study the relationship between the amplitudes of photodisintegration of the nonexcited and Pauli-allowed virtually excited b* = b/sub 1/+b/sub 2/ clusters in the nucleus A. The processes /sup 16/O(..gamma.., dd)/sup 12/C and /sup 12/C(..gamma.., pd)/sup 9/Be are examined.