The energy spectra of neutrons scattered by dilute solutions of chainlike molecules can throw light on the various types of molecular movements. Such a scattering experiment has been carried out using two low molecular weight (Zequals;3and 9) polymers of the polyhyphen;oxyhyphen;ethylene type dissolved in CS2, as scattering samples. The quasielastic part of the energy spectra has been analyzed in terms of the motion of the center of mass and that of the chain segments. The variation withZof the diffusion coefficientD(connected with the center of mass motion) indicates that the solventmdash;solute system interacts in the free draining limit. The constanta(related to the random motion of the chain segments) varies asqggr;with the exponent ggr; increasing withZ. It is also found that in both the cases studied, the value of ggr; is smaller than 4, the value predicted by de Gennes' theory for the case of molecules for whichZtends to infinity. The inelastic part of the spectrum has been analyzed in terms of the Kriegermdash;Nelkin approximation with a single effective mass. The effective mass obtained in the case of both scattering samples is much less than the real mass of the chain perhaps showing that the neutrons are sensitive to the rotation of the (CH2) groups. The agreement between the theory and experiment is not satisfactory in the inelastic case, indicating the need for a more sophisticated theory than the one used in our analysis.
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