Bewegungen der CH3-Gruppen in Methyl-Naphtalin-Kristallen .III.Protonenspin-Relaxation bei tiefen Temperaturen / Rotation of CH3 Croups in Methyl Naphthalene Crystals at low Temperatures

Abstract

In continuation of earlier works (temperature range 400 - 77 K) the temperature and frequency dependencies of the longitudinal relaxation time T₁ in different methyl naphthalene crystals were measured down to 4,2 K at 22 and 56 MHz. The observation of two minima in some cases below 50 K could be attributed quantitatively to the weakly hindered β-CH₃ groups (E_A <0,8 kcal/mole) by comparison of the results of similar methyl naphthalenes. The low relaxation rate in the minima is due to tunneling effects of the methyl groups. The splitting of the lowest torsional niveau could be roughly determined.