Abstract
The tunneling splitting of the NH4‐librational ground state in NH4ClO4 has been measured by high resolution inelastic neutron scattering at a temperature of 4.5 K. The spectrum shows four tunnel lines at energy transfers of 1.63±0.20, 4.06±0.20, 5.52±0.10, and 7.10±0.10 μeV. A discussion of the hindrance potential is given.