Electromagnetic radiation stretched transition

There are many types of interactions between electromagnetic radiation and matter. A species as a whole can change its rotational state the bonds (if any) within a species can bend, stretch, or twist and thus alto its vibrational state the electrons in the species may undergo transitions between various energy states and finally the atomic nuclei of the species can absorb energy from the incident radiation by making transitions between the different orientations to an externally imposed magnetic field. 

Section 13.20 IR spectroscopy probes molecular structure by examining transitions between quantized vibrational energy levels using electromagnetic radiation in the 625 000-cm range, where cm are units of wavenumbers, defined as Wavenumbers are proportional to frequency. The simplest vibration is the stretching of the bond between two atoms, but more complex vibrations can involve movement of many of a molecule s atoms. 

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