¹³C Nuclear Magnetic Resonance Spectroscopy:

¹H NMR spectroscopy is not the only helpful type of nmr spectroscopy. There are a large range of other isotopes that can be employed (for example ³²P, ¹⁹F, ²D). Though, the most frequently studied isotope apart from ¹H is the 13C nucleus. Such as protons, ¹³C nuclei have a spin quantum number of 1/2.  So, the same principles that apply to proton nmr also apply to ¹³C nmr. Though, whereas the ¹H nucleus is the naturally abundant isotope of hydrogen, the ¹³C nucleus is just only 1.1% naturally abundant. The meaning of this is that the signals for a ¹³C nmr spectrum are much weaker as compared to those for a ¹H spectrum. In the past, this was a problem because early nmr spectrometers calculated the absorption of energy as each nucleus in turn came into resonance. This was a long process and even though it was acceptable for ¹H nuclei, it meant that it was a very lengthy process for ¹³C nuclei since numerous thousand scans were essential in order to detect the signals above the background noise. Fortunately, this type of problem has now been overcome. Modern nmr spectrometers are much faster because all the nuclei are excited simultaneously with a pulse of energy. After that the nuclei are allowed to relax back to their ground state, emitting energy as they do so. This energy can be calculated and a spectrum produced. Consequently, ¹³C nmr spectra are now run regularly. At this spot, you may ask whether a ¹³C nmr spectrum also consist of signals for ¹H nuclei? The reply is that totally different energies are needed to resonate the nuclei of different atoms. Hence, there is no chance of seeing the resonance of a ¹H nucleus and a ¹³C nucleus in the limited range covered in a typical ¹H or ¹³C spectrum.