Presumption for a Quantum Energy Gap in the Quasi-One-Dimensional S = 1 Heisenberg Antiferromagnet Ni(C 2 H 8 N 2 ) 2 NO 2 (ClO 4 )

Magnetic susceptibility and inelastic neutron scattering experiments have been performed in the nearly ideal one-dimensional Heisenberg antiferromagnet with spin one, Ni(C2H8N2)2NO2ClO4. The experimental results are consistent with the recent theoretical predictions for a quantum energy gap between the ground state and the first excited states.