Differences and Similarities between Raman Spectroscopy

1、 Similarities:
(1) For certain given chemical bonds, their infrared absorption frequency and Raman shift are essentially equal, both representing the energy of the first vibrational level. Therefore, for certain given compounds, the infrared absorption wave numbers and Raman shifts of certain peaks are exactly the same;

(2) The infrared absorption wavenumber and Raman shift are both in the infrared region, reflecting the structural information of the molecule. Raman spectroscopy, like infrared spectroscopy, is also used to detect the vibrational and rotational energy levels of material molecules.

1、 Differences:

(1) Fundamental difference: Infrared spectroscopy is absorption spectroscopy, while Raman spectroscopy is scattering spectroscopy;

(2) Infrared is easier to measure and has a stronger signal, while Raman signals are weaker and have lower resolution. However, Raman spectra have few overlapping bands, making spectral analysis more convenient;

(3) Infrared spectroscopy uses infrared light (especially mid infrared light), while Raman spectroscopy can choose from visible light to near-infrared light;

(4) Infrared spectroscopy is commonly used to study the asymmetric vibrations of polar groups, while Raman spectroscopy is commonly used to study the symmetric vibrations of non-polar groups and skeletons;

(5) Raman spectroscopy can measure aqueous solutions (water has weak Raman scattering), while infrared spectroscopy is not suitable for measuring aqueous solutions;

(6) Raman spectroscopy does not require special sample preparation, while infrared spectroscopy requires sample preparation;


(7) Raman spectroscopy can be measured in glass containers or capillaries, but infrared spectroscopy cannot be measured in glass containers;

(8) Raman spectroscopy and infrared spectroscopy often complement each other, namely: strong infrared, weak Raman, weak infrared, strong Raman;

(9) Infrared spectroscopy is more effective in identifying organic compounds, while Raman spectroscopy provides more comprehensive information on inorganic compounds;

(10) Infrared spectroscopy analysis: three elements (absorption frequency, intensity, peak shape), Raman spectroscopy analysis includes depolarization degree in addition to the three elements.