Isospin Sum Rules and the Photodisintegration of theA=3Nuclei

Three sum rules for the electric dipole photodisintegration cross section of the $A=3\mathrm{}$ nuclei are split into their final-state isospin components. The isospin doublet contribution to the three-nucleon breakup mode is estimated to be of the order of 10-20% and originates primarily in the high-energy region.