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In molecular vibrational spectroscopy, a hot band is a band centred on a hot transition, which is a transition between two excited vibrational states, i.e. neither is the overall ground state. In infrared or Raman spectroscopy, hot bands refer to those transitions for a particular vibrational mode which arise from a state containing thermal population of another vibrational mode. For example, for a molecule with 3 normal modes, ν 1 {\displaystyle \nu _{1}} , ν 2 {\displaystyle \nu _{2}} and ν 3 {\displaystyle \nu _{3}} , the transition 101 {\displaystyle 101} ← 001 {\displaystyle 001} , would be a hot band, since the initial state has one quantum of excitation in the ν 3 {\displaystyle \nu _{3}} mode. Hot bands are distinct from combination bands, which involve simultaneous excitation of multiple normal modes with a single photon, and overtones, which are transitions that involve changing the vibrational quantum number for a normal mode by more than 1.