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1. The branch of spectroscopy concerned with the measurement of the intervals between atomic or molecular energy levels that are separated by frequencies from about 105 to 109 hertz, as compared to the frequencies that separate optical energy levels of about 6 × 1014 hertz.
   "Radio-frequency spectroscopy of nuclei in a magnetic field has been employed in a medical technique called magnetic resonance imaging (MRI) to visualize the internal soft tissue of the body with unprecedented resolution."

Type of: spectrographic analysis, spectrometry, spectroscopic analysis, spectroscopy, spectrum analysis