Inelastic neutron scattering of methyl tunnelling in isotopic mixtures of dibromomesitylene
In dibromomesitylene, only the methyl group denoted Me-2 and surrounded by two bromine atoms, is a quasi free rotor. In isotopic mixtures the Me-2 tunnelling gap is almost insensitive to variations in temperature and to isotopic dilution. The Me-2 hindering potential remains the same as in the pure material with a main component cos6 theta. Because there is no coupling between the methyl groups, d