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Fluorescence Spectra of Uranyl Ion in Various Environments

April 12, 2004

Chifuru Noda and Laura Kinnin

All of the following spectra pertain to the various solid state environment that uranyl (UO2 2+) ion is found, except the one labelled "aqueous". These spectra were taken on a Perkin-Elmer Fluorescence Spectrometer at Bridgewater State College. The purchase was made possible by the grant from the Shoolman Foundation, and the support is gratefully acknowledged.

FYI: 510 nm is usually considered as "green". The orange street lamp (sodium lamp) is about 600 nm. A red laser pointer is around 650 nm. Blue is around 450 nm.

Technical: The excitation wavlength is 300 nm, which seems to give the strongest fluorescence and the minimum reflection from the surface. The resolution is 10 nm (the width of slits at the excitation and emission spectrometers).

Pure Uranyl Compounds

Autunite and Unranocircite are a pure uranyl compound, and it shows the distinct vibrational bands. These are very similar to the opal spectrum shown in "Ultraviolet Light and Fluorescent Minerals" by Warren, Gleason, Bostwick and Verbeek (page 161). Autunite is from Spokane Co, WA, and Uranocircite is from Bergen Vogtland, East Germany.

Andersonite is another pure uranyl compound, and it also shows the distinct vibrational bands. Compared to the autunite and uranocircite spectra, this andersonite spectrum is shifted to a shorter wavelenth hinting that the andersonite fluorescence is bluer, which agrees with eyeball observation. Andersonite is from Kane Springs Wash, San Juan Co, UT.

The aqueous spectrum was taken for a solution of uranyl acetate. It shows some structure, but it is blurred, possibly because of the relaxation process due to loosely bound water molecules.

Uranyl Salts in Glass (aka, uranium glass, vaseline glass)

The next two spectra were taken for uranium glass. The first is a vaseline glass from Depression era. Under daylight, it is green. The second is for a recent vaseline bead, which is yellowish under daylight. Note that there is no structure.

Uranyl as Impurities

These spectra were for various minerals that are either coated with uranyl compounds, or includes uranyl compounds as impurity.

These fluorescence spectra show somewhat less prominent but still discernible peaks:

Aragonite (from Santa Eulalia District, Chihuahua, Mexico)

Geode (which looks like a frog; locality unknown)

Adamite (from Mina Ojuela, Mapimi, Durango, Mexcio)

Youngite (from Wyoming)

Uranyl as Impurities (Hyalite Opal)

Various hyalite opal specimens also show similar structure:

Hyalite Opal (crust) from Spruce Pine, NC shows bright blueish green fluorescence from the crust.

Hyalite Opal (slab) from unknown locality contains uranyl as impurity.

Hyalite Opal (glass-like) from Valec, Czech Republic is very weak, and quite noisy. Its "structure" is questionable, and the band at 430 nm is probably a contamination (fingerprint or paper lint). This hyalite opal is almost glass-like, and is transparent and colorless. It shows very weak green fluorescence under UV.