![refractive index database refractive index database](https://www.researchgate.net/publication/340349788/figure/download/fig3/AS:907102872666118@1593281586659/Refractive-index-n-Al2O3-of-Al-2-O-3-layers-deposited-at-different-vacuum-conditions.jpg)
Finally, the refractive index of the compressed sample is crucially needed to extract the accurate shock EOS data in shock compression experiments using optical velocimetry 30, 31, 32. Brillouin spectroscopy measurements with 90° and 180° scattering geometries require the refractive index to calculate the sound velocity and elastic properties of sample from the raw data 27, 29. Compression-induced electronic transitions, like band-gap closure and metallization, have also been investigated by analyzing the dispersion 15, 16, 17, 23.
![refractive index database refractive index database](http://www.process.mtl.kyoto-u.ac.jp/mult/refr1.gif)
One can also use the measured pressure dependence of the refractive index to estimate the density change using the Lorentz–Lorenz relation with the assumption of a constant molecular polarizability 27. With known refractive index, sample thickness in the DAC can be estimated for the further evaluations of the volumetric strain and equation of state (EOS) as well as for the detection of phase transitions 12, 22. Rates of refraction, reflection, and attenuation are considered when calculating the refractive index of transparent media, which tends to fall between 1 2 n.Continued innovations with photonic technology such as light-emitting diodes (LEDs) and organic light. Refractive index at high pressure has been extensively investigated using diamond anvil cells (DACs) 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28. A refractive index is an indicator of how different frequencies and wavelengths of light propagate through a transparent material. Measuring the refractive index accurately is therefore a powerful, contact-less way to probe how pressure alters the electronic charge distribution and the inter-atomic/molecular distances. The variations of the refractive index with photon energy, called the dispersion, can be used to reveal electronic properties such as the band gap energy 7, 8, 9. In electro-magnetic theory, the complex refractive index can be defined as the square root of the complex relative dielectric constant 1, 2. Empirically, it has been found to correlate strongly with other material properties such as density and polarizability 3, 4, 5, 6. By definition, the refractive index n determines the phase velocity of the electromagnetic wave in a given material v compared to the speed of light in vacuum as \(n = c/v\). It reflects the dynamic polarization of atoms and/or molecules under electromagnetic radiation inducing oscillations of electron clouds and/or rotations of polar molecules 1, 2.
![refractive index database refractive index database](https://www.pirika.com/images/RI2.jpg)
Refraction is one of the most common optical phenomena, indicating the bending of non-perpendicular incident waves at the interface between two different media.