There are many spectroscopic techniques applicable to the identification and measurement of molecular species (including polyvalent ions and metal–ligand complexes). These can be grouped in different ways, and applied – with varying degrees of complexity – to the study of gas, liquid, and solid phase samples. The following table provides a short summary of the principle molecular spectroscopy techniques used in analytical chemistry:
| Technique | Mode | Spectral Region | Energy Transition | Sample phase |
|---|---|---|---|---|
| Absorption (UV-Vis) | absorption, reflectance | UV &
visible (near IR) | electronic (vibrational) | solution (gas) |
| Fluorescence | emission (luminescence) | UV & visible | electronic (vibrational) | solution (solid) |
| Phosphorescence | UV & visible (near IR) | electronic (vibrational) | solution (solid) | |
| Fourier transform infrared | absorption, reflectance | IR | vibrational (rotational) | solid, gas (solution) |
| Raman | scattering | solid, solution | ||
| Microwave | absorption | microwave | rotational | liquid, solution |
| Electron Spin Resonance | radio wave | electron spin state | solution, liquid, solid | |
| Nuclear Magentic Resonance | nuclear spin state |