EPR, optical, infrared and Raman spectral studies of Actinolite mineral

Our plain-English summary of EPR, optical, infrared and Raman spectral studies of Actinolite mineral, by N.O. Gopal, K.V. Narasimhulu, J.L. Rao (Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy, 2004).

The study

• Authors: N.O. Gopal, K.V. Narasimhulu, J.L. Rao
• Journal: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
• Published: 2004;60(11):2441-8
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Electron paramagnetic resonance (EPR), optical, infrared and Raman spectral studies have been performed on a natural Actinolite mineral. The room temperature EPR spectrum reveals the presence of Mn(2+) and Fe(3+) ions giving rise to two resonance signals at g = 2.0 and 4.3, respectively. The resonance signal at g = 2.0 exhibits a six line hyperfine structure characteristic of Mn(2+) ions. EPR spectra have been studied at different temperatures from 123 to 433 K. The number of spins (N) participating in the resonance at g = 2.0 has been calculated at different temperatures. A linear relationship is observed between log N and 1/T in accordance with Boltzmann law and the activation energy was calculated. The paramagnetic susceptibility (chi) has been calculated at different temperatures and is found to be increasing with decreasing temperature as expected from Curie's law. From the graph of 1/chi versus T, the Curie constant and Curie temperature have been evaluated. The optical absorption spectrum exhibits bands characteristic of Fe(2+) and Fe(3+) ions. The crystal field parameter Dq and the Racah parameters B and C have been evaluated from the optical absorption spectrum. The infrared spectral studies reveal the formation of Fe(3+)--OH complexes due to the presence of higher amount of iron in this mineral. The Raman spectrum exhibits bands characteristic of Si--O--Si stretching and Mg?OH translation modes.

In plain English

This was a laboratory physics study of one natural sample of actinolite. The authors describe actinolite as an asbestiform mineral of the amphibole group. The sample came from Wenatchee Ridge in the Cascade Range, Washington, USA. The study did not examine people, animals, exposure or health. The authors measured how the powdered mineral responded to microwaves in a magnetic field (EPR), to visible and ultraviolet light, and to infrared radiation, and how it scattered laser light (Raman). A chemical analysis found impurities of 2% iron, 0.2% manganese, 0.05% cobalt, 0.2% chromium and 0.2% nickel. The authors attributed the EPR signals to manganese (Mn2+) and iron (Fe3+) ions. Measurements from 123 to 433 K gave an activation energy of 0.0082 eV, a Curie constant of 0.175 emu/mol and a Curie temperature of 77 K. Light absorption showed iron in two forms (Fe2+ and Fe3+) and an optical band gap of 3.14 eV. The authors linked infrared bands to iron–hydroxyl complexes and Raman bands to silicon–oxygen and magnesium–hydroxyl vibrations.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory spectroscopic study (EPR, optical absorption, infrared and Raman spectroscopy) of a powdered natural mineral sample; not a health study
• Who was studied: A single natural actinolite mineral sample collected at Wenatchee Ridge, Cascade Range, Washington, USA; no people or animals were studied
• Exposure: No exposure of people or animals was studied. The material analysed was actinolite, which the authors describe as an asbestiform mineral of the amphibole group
• Main results:
  • Chemical analysis of the actinolite sample found 2% iron, 0.2% manganese, 0.05% cobalt, 0.2% chromium and 0.2% nickel as impurities
  • The EPR spectrum showed two signals, which the authors attributed to manganese (Mn2+) ions and iron (Fe3+) ions
  • The authors judged the bonding between manganese and its surrounding atoms to be moderately ionic
  • EPR spectra were recorded at temperatures from 123 to 433 K, giving an activation energy of 0.0082 eV
  • The Curie constant was 0.175 emu/mol and the Curie temperature was 77 K
  • The optical absorption spectrum showed iron in both divalent (Fe2+) and trivalent (Fe3+) states, plus a charge-transfer band between them
  • The optical band gap energy was 3.14 eV
  • The authors attributed infrared bands to metal ion–hydroxyl vibrations, and Raman bands to silicon–oxygen–silicon stretching and magnesium–hydroxyl modes
• The authors' conclusion: The authors concluded that the actinolite sample contained manganese (Mn2+) and iron (in both Fe2+ and Fe3+ states), and that its EPR, magnetic, optical, infrared and Raman properties were as listed in their results. They drew no conclusions about health

Topics

The National Library of Medicine indexes this study under subjects our site covers: Actinolite.

Medical terms in this study, explained in our Lexicon: Actinolite.

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