Free fatty acid (FFA) is one of the most critical parameters for evaluating the quality of olive oil. In this paper, we present a simple and rapid Raman spectroscopy method for analyzing free fatty acid in olive oil. First, FFA degradation of carotenoids in olive oil is confirmed by analyzing the relative intensity of characteristic vibrational modes and introducing an intensity decrease factor. Second, it is demonstrated that the relative intensity ratio of the two characteristic vibrational modes at 1525 cm⁻¹ and 1655 cm⁻¹ presents a good and rapid analysis of FFA content in olive oil; the relative intensity ratio decreases linearly with FFA content. In addition, resonance Raman scattering of carotenoid is discussed, showing that a green laser should be utilized to study FFA in olive oil.

Raman spectroscopy has been applied to study unsaturated fatty acid in edible vegetable oils. The relative intensity ratio of characteristic vibrational bands has been investigated as a function of the content of totally unsaturated fatty acid, polyunsaturated fatty acid, and monounsaturated fatty acid. The results suggest the intensity ratio of 1655 cm⁻¹ to 1440 cm⁻¹ or 1265 cm⁻¹ to 1300 cm⁻¹, i.e., a characteristic vibrational band correlated with carbon-carbon double bond in acid chain to a vibrational band not correlated with double bond, could be applied for preliminary analysis of the content of polyunsaturated fatty acid or monounsaturated fatty acid, but cannot be used to analyze the content of total unsaturated fatty acid. Additionally, two-dimensional correlation spectroscopy (2DCOS) has been performed on the content dependent Raman spectra. The 2DCOS result is consistent with that by Raman spectroscopy.

Impurity‐induced structural distortion in SmB₆ is suggested by Raman spectroscopy study on impurity‐controlled samples. Significant differences in the Raman spectra of single crystals SmB₆(6N), synthesized with 99.9999%‐pure boron, and SmB₆(3N), synthesized with 99.9%‐pure boron, are detected. While no noticeable differences are detected in the X‐ray diffraction of SmB₆(3N) and SmB₆(6N), all the Raman phonon modes of the T_2g, E_g, and A_1g of SmB₆(3N) are clearly broader and shift to higher wavenumbers than those of SmB₆(6N), and the T_2g and E_g modes of SmB₆(3N) show doublet features. Based on the high‐pressure Raman measurements and phonon calculation in uniaxial compression model, we argue that small amount of impurities in SmB₆(3N) is enough to induce anisotropic distortion in the B₆ octahedra, leading to peculiar behaviors in Raman spectrum of SmB₆(3N). Our results may present a clue for understanding the current puzzles about SmB₆ of various origins with different impurities.