In an NMR experiment, a large magnetic field is applied to the sample. This causes the nuclear spins to become aligned. A radio wave at the proper frequency will provide enough energy to flip the spin from being aligned with the field to being anti-aligned. This frequency will depend on the chemical environment of the atom. By measuring these frequencies, one can learn about the structure of the molecule.
Jeol Eclipse 300 MHz FTNMR with auto-tune, broad-band dual probe, 1H-19F/X capability.
Varian Unity Inova 400 MHz FTNMR with tunable, broad-band dual probe, 1H-19F/X capability (donated by Pfizer, Holland)