The orientational memory from three-time correlations in multidimensional NMR experiments

We elucidate the presence of correlated back-and forth-jumps of polymer seg ments close to the glass transition. An analytically tractable model is int roduced which allows to quantify the back-jump probability and hence the or ientational memory. The relation to the important question of heterogeneous and homogeneous dynamics close to the glass transition is outlined. Applic ation to two different polymers shows that the back-jump probability is clo se to 30%. (C) 1999 Elsevier Science B.V. All rights reserved.