Recent experiments on ${\left(\mathrm{T}\mathrm{a}{\mathrm{Se}}_4\right)}_2$I and ${\mathrm{K}}_{0.3}$Mo${\mathrm{O}}_3$ have established the existence of three separate ac conductivity resonances associated with the pinned charge-density waves (CDW's) in these quasi-one-dimensional materials. We propose a detailed interpretation of these modes in terms of the three different length scales which appear in our recent strong-pinning theory of CDW dynamics. Quantitative estimates are obtained for all three characteristic frequencies in good agreement with experiment.

• Received 21 March 1988

DOI:https://doi.org/10.1103/PhysRevB.38.4303