Redistribution of electronic charges in spin-Peierls state in (TMTTF)(2)AsF6 observed by C-13 NMR

We report C-13 NMR spectra and nuclear spin lattice relaxation rate 1/T-1 for a quasi-one-dimensional quarter-filled organic material (TMTTF)(2)AsF6, which undergoes charge ordering (T-CO = 102K) and spin-Peierls phase transitions (T-SP = 14 K). The ratio of two 1/T-1, for the charge accepting and donating TMTTF sites which brows from T-CO finally saturates in approaching T-SP, indicating one spin correlation function even in the charge ordered state. Below T-SP, however, the doubly split NMR lines from inequivalently charged molecules merge into one line, originated from the variation in charge densities. This shows that a rearrangement of the charge configuration occurs at T-SP.