%0 Journal Article %J Chemical Physics Letters %D 1993 %T Squid-Nmr Study of Methyl Quantum Tunneling in a Series of Carboxylic-Acids %A Black, B. %A Majer, G. %A Pines, A. %K nuclear %X

Quantum tunneling frequencies of methyl groups at low temperature can be measured directly by low-field nuclear magnetic resonance (NMR) using our dc-SQUID (superconducting quantum interference device) spectrometer. From NMR spectra recorded in magnetic fields below 20 mT, tunneling frequencies between 140 and 250 kHz were measured for a homologous series of carboxylic acids at 4.2 K. For solids with equivalent crystal structures, we observe an exponential correlation between the tunneling frequency and the enthalpy of fusion; from this correlation we obtain information about the contribution of intermolecular interactions to the energy barrier for methyl rotation.

%B Chemical Physics Letters %V 201 %P 550-554 %8 Jan 8 %@ 0009-2614 %G English %U ://WOS:A1993KF75400026 %N 5-6 %M WOS:A1993KF75400026 %! Squid-Nmr Study of Methyl Quantum Tunneling in a Series of Carboxylic-Acids %R Doi 10.1016/0009-2614(93)85115-5