For the vibrational spectra of trans-(CH)x and Cis-(CH)x, in the region of weak electron-lattice coupling λ, the λ-dependences of optical phonons ω0(k = O) of these two isomers obey different rules. This is due to the existence of 3 confined potential barrier in the cis-(CH)x and thus causes the ground state to be non-degenerate.