Laser-induced REE3+ photoluminescence of selected accessory minerals — An “advantageous artefact” in Raman spectroscopy

Abstract

Keywords:Zircon Xenotime Monazite Titanite Laser-induced REE photoluminescence Raman artefact Laser-induced photoluminescence of trivalent rare-earth elements (REEs), which is obtained as analytical artefacts in Raman spectra of selected accessory minerals, was studied. Spectra of natural titanite, monazite-(Ce), xenotime-(Y), and zircon samples from various geological environments were compared with emission spectra of synthetic, flux-grown analogues doped with REEs. The latter is of great importance to identify potentially mistakable bands as either Raman or PL signal, and to assign them to certain REE centres. In the samples investigated, various REE centres are excited selectively using 473, 514, 532, 633, and 785 nm laser excitation. Their assignment was verified by photoluminescence-excitation experiments. Luminescence spectral patterns of zircon and titanite vary in dependence of trace-REE concentrations, hence reflecting geochemical growth conditions. "REE artefacts" in Raman spectra of accessory minerals may be used as fingerprint tool for mineral phaseidentification. The distribution of REE emission-intensities, revealed by hyperspectral mapping, opens up the opportunity to visualise mineral textures, complementary to cathodoluminescence imaging-techniques.

Sequentially shifted excitation: A tool for suppression of laser‐induced fluorescence in mineralogical applications using portable Raman spectrometers

“…Additionally, a steeply rising fluorescence background consisting of many bands begins below 900 cm −1 , a region in which some of the zircon Raman bands occur. Using the 785 nm excitation, the fluorescence pattern is similar to the data reported by Lenz et al, 2015 . They attributed the fluorescence bands below 500 cm −1 to the 3 H 4 → 3 H 6 electronic transition of the Tm 3+ ions, and the 1,200–1,600 cm −1 region to the 4 F 3/2 → 4 I 9/2 electronic transition of the Nd 3+ ions.…”

“…The Raman spectra of zircon sample Zi2 are similar to the spectra of the Zi3 sample for both the standard and SSE excitation instruments. The Zi2 sample was the only one that manifested fluorescence when analyzed with the 532 nm portable instrument; several bands in the 500–900 cm −1 range are consistent with the data from Lenz et al, 2015, in which the authors attributed these bands to the 4 S 3/2 → 4 I 15/2 electronic transitions of the Er 3+ ions. A similar group of fluorescence bands were observed in the spectra taken with the 514 nm laboratory instrument, only having been shifted to a higher value on the Raman shift scale (see Table ), while retaining their absolute wavenumber position.…”

Gadolinite-(Nd), a new member of the gadolinite supergroup from Fe-REEdeposits of Bastnäs-type, Sweden

“…Raman spectra of REE-bearing minerals are commonly obscured by laser-induced emissions of the REE (e.g. Nasdala et al, 2012;Lenz et al, 2015). After careful tests with different lasers (473, 523 and 633 nm), the 633 nm He-Ne laser (10 mW …”

GZ7 and GZ8 – Two Zircon Reference Materials for SIMS U‐Pb Geochronology

“…, Lenz et al . ), which in turn are controlled by the particular electronic structure of each REE ion (Dieke and Crosswhite , Reisfeld and Jørgensen ). Following Lenz and Nasdala (), the FWHMs of the ~ 17210 cm −1 sublevel of the 4 F 9/2 → 4 H 13/2 emission of Dy 3+ and the ~ 11360 cm −1 sublevel of the 4 F 3/2 → 4 I 9/2 emission of Nd 3+ (Figure b) were used to estimate the degree of radiation damage.…”

“…As reference analyses, PL measurements were also done on REE 3+ ‐doped ZrSiO 4 crystals grown using a Li‐Mo flux technique (for details see Lenz et al . , and references therein). Line scanning across the large slices was done using a software‐controlled Märzhäuser SCAN x – y stage.…”