Raman Spectroscopy Overview The RRUFF™ Project collects spectral data from minerals using Raman spectroscopy, which reveals characteristic traits based on the behavior of the chemical bounds under laser excitation. (Read more about the theory of Raman scattering.)

Above left: Student on Thermo Almega XR. Above center: Ahura FirstDefender. Above right: Translation and rotation stage for measuring oriented Raman.

Our systems have been calibrated to ensure that the database remains self-consistent. Though Raman shift is independent of wavelength, fluorescence is not, so data is collected using lasers occupying both the red and green regions of the visible spectrum.

Mineral samples are mounted onto a stage taking care to ensure that the path of the laser is orthogonal to the surface to be measured. To obtain spectra from oriented samples we built a high-precision translation and rotation stage and goniometer for the optical bench. The laser energy excites the material, causing the bonds to vibrate. Laser light is reflected back off of the surface, and along with it is emitted light of a wavelength shifted from that of the laser.

This Raman signal is only one millionth the intensity of the reflected laser light. The laser light is filtered out, leaving only the faint Raman signal to pass through to the detector. The data gathered is in the form of peaks at wavelengths shifted relative to the laser. These peaks act as a fingerprint as they are unique to the mineral because they are the result of vibration along the bonds of the crystal structure, which is also unique to the mineral.

After data collection, background is reduced, and cosmic ray events are removed using CrystalSleuth. Spectra collected are compared to those already in the database, then posted online.

Visit CrystalSleuth Help or find out how to use CrystalSleuth to analyze your Raman spectra with the Raman Quick Start guide on the "Basics" page.