ELECTRON-NUCLEAR DOUBLE-RESONANCE STUDIES OF PRISTINE AND C-13-ENRICHED POLYACETYLENE

Electron-nuclear double resonance (ENDOR) and electron-nuclear-nuclear triple resonance (TRIPLE) spectra of pristine cis-rich (CH), at low temperatures are consistent with the spin density distribution of the soliton predicted for a finite electron correlation. The ratio of the peak value of the negative spin density rho(1) to that of the positive spin density rho(0) is determined to be rho(1)/rho(0) approximately -0.44 with the aid of ENDOR-induced ESR measurements. On the other hand, intrinsic ENDOR spectra due to the soliton spin density is not observable in C-13-enriched samples because of the line shape distortion caused by the overlapping second-harmonic signal of C-13 nuclear frequency and other structures at frequencies related to H-1 and C-13 nuclear Larmor frequencies.