Observation of Spin-Torsional Spectrum through Nuclear Magnetization Time Evolution in the Rotating Frame

A new experimental technique is introduced by which tunneling splittings of ground torsional-oscillator states in solids can be obtained directly. Rotating-frame time evolution of the spin-torsional system, monitored by the proton spin magnetization, is presented for N${\mathrm{H}}_4$I and C${\mathrm{H}}_3$C${\mathrm{D}}_2$I, along with the frequency spectra. The resolution of the spectral lines is an order of magnitude better than the magnetization-loss spectra.