Laser excitation spectroscopy of beryllium heat treatment in synthetic ruby

Ruby is a gem variety of corundum (α-Al2O3) that is colored red by trivalent chromium (Cr3+) substituting for Al3+ in the corundum structure. Recently, the beryllium (Be) heat treatment has been practiced as a technique to enhance the color of ruby. The ruby will turn orange to be an orange sapphire as a result of the enhancement. Some advanced technics to identify the Be heat-treated orange sapphire have been developed such as laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser-induced breakdown spectroscopy (LIBS). We studied the effect of Be atoms in the corundum structure using the red, green, blue and purple laser excitation spectroscopy with the wavelengths of 634 nm, 545 nm, 452 nm and 408 nm respectively. The fluorescence spectra were analyzed for unheated, normal heat treatment and Be heat treatment synthetic ruby samples. The fluorescence intensity of the Be-heated samples was lowest compared to the unheated and normal treated ones for both high and low Cr content.