Raman spectroscopy of lithium hydride corrosion: Selection of appropriate excitation wavelength to minimize fluorescence

Abstract

Lithium hydride is pyrophoric and will efficiently react with moisture forming lithium hydroxide on the surface. Typically, this surface corrosion reaction is examined by diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy. In the current study, Raman spectroscopy has been used to evaluate the same reaction with a focus on the role of Li2O in particular. A number of visible and near infrared excitation lasers were investigated in order to achieve the highest sensitivity; however, fluorescence dominates the spectrum. Photo bleaching experiments resulted in fluorescence reduction after illumination. Photoluminescence spectra indicate that the UV excitation could provide a luminescence-free region to collect high quality Raman spectra for LiH. A custom Raman probe was used to study the hydrolysis reaction of LiH with a 325nm laser. Further, the role of lithium oxide in the hydrolysis kinetics has been studied.