In a normal (hydrogenated) pentacene molecule, 14 protons give rise to a broad and complex hyperfine lineshape, thus to a broad ODMR line. If all protons are replaced by deuterons, which have a 6-times weaker magnetic moment, the ODMR line becomes 36 times narrower. Now, if our molecule contains a single proton – and 13 deuterons – or a single 13C atom – and 19 12C atoms – the ODMR line will be split by interaction with this spin 1/2. The split line is now a probe for the state of a single nuclear spin [1], whose magnetic moment is a thousand times weaker than that of a single electron! In later experiments by J. Wrachtrup and the group of C. von Borczyskowski in Chemnitz, the spin state of the nucleus was manipulated with a radio frequency. This led to the first nuclear magnetic resonance experiment on a single nucleus [2]
- J. Köhler, A.C.J. Brouwer, E.J.J. Groenen, J. Schmidt
“Single molecule electron paramagnetic resonance spectroscopy: Hyperfine splitting owing to a single nucleus”
Science 268 (1995) 1457-1460 - J. Wrachtrup, A. Gruber, L. Fleury, C. von Borczyskowski
“Magnetic resonance on single nuclei”
Chem. Phys. Lett. 267 (1997) 179-185