Proton motion in some hydrogenous liquids studied by cold neutron scattering

Abstract

Using the cold neutron time-of-flight spectrometer at the Stockholm reactor a series of hydrogenous liquids have been investigated. The diffusive motions in the liquids as well as their spectra of hindered translations and rotations are investigated in great detail. It is found that the neutron is very sensitive to the rate determining process of the proton motion. Relaxation times for various motions of the protons in and between the molecules are determined. It is found that the mean life time of a hydrogen bond is in the range 10 -11 to 10 -12 seconds for the liquids investigated. Similarly the activation energy for the motion of the protons is determined in various temperature regions. It is shown that the diffusion process may be described as a simple random walk process after a time of about 10 -12 seconds has elapsed. Comparison of the experimental results to various theories for neutron scattering from liquids is performed. The results of the relaxation time studies are compared to experimental results of dielectric ultrasonic and nuclear magnetic relaxation time studies. It is shown that very probably a cluster formation of molecules occurs and the size of these clusters as a function of temperature is indicated.