Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

A kind of spectroscopy that is the main application of this phenomenon depends on chemical shifts arising from partial shielding of atoms or molecules by electrons. The surrounding electrons cause atoms to absorb radiation at slightly different field strengths for a fixed frequency. Atoms may only absorb radiation at photon energies equal to the difference between energy levels as determined by a characteristic spin, resulting in quantized orientations of the magnetic moment vector. FTP, what is this absorption of radiation at a precise frequency by nuclei with a nonzero spin that causes them to behave like small magnets

Science