A DIRECT OBSERVATION OF TUNNELING STATES IN MOLECULAR-SOLIDS WITH RANDOM INTERNAL STRAINS

Inelastic-neutron-scattering experiments on ternary salts (NH4)(0.02)R bxK0.98-xI for x = 0.0, 0.05, 0.1 and 0.5 have been carried out at 4 K . The gradual buildup of intensity in the range 0 to 0.6 meV with incr easing values of x suggest that, beyond a certain Value of x, these sy stems might show a low-temperature two-level system behaviour and that the tunnelling defects responsible for this might well be the NH4+ io ns present in them. This has been confirmed by specific-heat measureme nts down to 0.7 It on the maximally strained (x approximate to 0.5) sy stem.