Fcc/bcc metals do not show Raman spectra.
However, I have studied pure gold with Raman (532 nm laser, 30 mW on sample) and found a strong and asymmetric band at 76.0 ± 1.1 cm-1. Natural gold shows the same band. How can this band be interpreted?
Dear Rainer Thomas ,
Read the next article's first part (It cannot be mentioned more):
Article Gravity a paradym shift in reasoning
I want to know that it helped you.
Regards,
Laszlo
Dear Laszlo,
Thank you very much for your lovely article. I have read it, and the article has made me thoughtful. I have performed new experiments with pure gold, silver, copper, and zirconium. Au, Ag, and Cu are face-centered cubic (fcc), and Zr is hexagonal close-packed (hcp). The first three elements contain only a single atom in the primitive unit cell and should have no optical phonons. Result: these elements have no first-order Raman bands.
The unit cell of zirconium contains two atoms and has a hexagonal close-packed (hcp); therefore, optical phonons will exist). Result: hcp metals do have a Raman spectrum, so also zirconium.
However, these points are not the answer to my question. All studied metals have shown in the experiment an anomaly and strong, a bit asymmetric band at about 76.0 ± 1.1 cm-1, nearby independent of the metal. In the case of copper, the oxidation state is essential. On a fresh surface, copper behave like Au and Ag. Oxidation increases the band's width, decreases the intensity, and increases the asymmetry significantly. Also, the reflection quality increases the intensity.
In comparison with the intensity of the laser (532 nm) in the zero position, the band's intensity at 76 cm-1 is only about 7.8 % of the primary one. I interpret the 76 cm-1 bands in the Raman spectrum as a result of a weak light component in the laser with a slightly different wavelength.
Is such an interpretation conceivable?
Remark:
During Raman spectroscopic studies of silicates and aqueous solutions, the described effect has practically no meaning. However, the "extra" Raman band can help identify small gold particles in fluid inclusions.
Best regards,
Rainer
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