Final answer:
NMR spectra can be generated for certain types of nuclei when placed in an external magnetic field. The specific frequency of absorbed and reemitted radio waves depends on the type of nucleus, the chemical environment, and the external magnetic field strength.
Step-by-step explanation:
NMR spectra can be generated for certain types of nuclei. When placed in an external magnetic field, these nuclei align into new energy states based on their spin orientation. By using an external radio frequency signal to flip the orientation, transitions between energy states occur, resulting in the absorption and reemission of specific frequencies. This phenomenon is known as nuclear magnetic resonance (NMR). The specific frequency depends on the type of nucleus, the chemical environment, and the external magnetic field strength.