We find the exact ground-state wave function of an open S=1/2 spin chain with exchange that scales in inverse proportion to the square of the sum and the difference of the coordinates of the spins. For isotropic exchange interaction, numerical study reveals that in common with the periodic manifestation of the spin model, the states are grouped into highly degenerate multiplets.

• Received 17 January 1994

DOI:https://doi.org/10.1103/PhysRevB.50.1102