Manganese valency and the colour of the Mn2AsO4(OH) polymorphs eveite and sarkinite

1998 ◽  
Vol 62 (1) ◽  
pp. 113-119 ◽  
Author(s):  
Ulf Hålenius ◽  
Erika Westlund
Keyword(s):  
Optical Absorption ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Octahedral Site ◽  
Optical Absorption Spectra ◽  
Absorption Bands

AbstractPolarized optical absorption spectra of single crystals of the two dimorphic Mn2AsO4(OH)-minerals eveite and sarkinite show that minor concentrations of Mn3+ at the octahedral site determine the colour and cause the distinct pleochroism in green and yellow of eveite. In the sarkinite spectra only absorption bands due to spin-forbidden d-d transitions in Mn2+ at six- and five-coordinated sites are observed, which produce a weak flesh-red mineral colour and a very faint pleochroism.

Excitonic Bands in the Optical Absorption Spectra of A3MX6 and A3M2X9 (A = MeNH3, Me2NH2, Me3NH, Me4N; M = Bi, Sb; X = Cl, Br, I)

1994 ◽  
Vol 49 (6) ◽  
pp. 849-851 ◽  
Author(s):  
G. C. Papavassiliou ◽  
I. B. Koutselas
Keyword(s):  
Optical Absorption ◽  
Absorption Spectra ◽  
Spectral Region ◽  
Visible Spectral Region ◽  
Optical Absorption Spectra ◽  
Absorption Bands ◽  
Uv Visible ◽  
Low Dimensional

The title compounds (natural low-dimensional semiconductors) show strong excitonic optical absorption bands in the UV-visible spectral region, because of the dielectric confinement of excitons. as in the cases of other similar systems based on PbX2-4, SnX2-4. PtI - X - PtIV-X , Cdx,Sy-clusters etc

Optical Absorption Spectra of Substituted Methylenes Oriented in Single Crystals

1966 ◽  
Vol 44 (1) ◽  
pp. 413-414 ◽  
Author(s):  
Gerhard Closs ◽  
Clyde A. Hutchison ◽  
Bryan E. Kohler
Keyword(s):  
Optical Absorption ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Optical Absorption Spectra

scholarly journals Optical Studies on KBr:Tl and KCl-Br:Tl Mixed Crystals

2010 ◽  
Vol 7 (2) ◽  
pp. 425-432
Author(s):  
P. Eswaran ◽  
A. Anbagi ◽  
S. Nagarajan
Keyword(s):  
Optical Absorption ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Emission Band ◽  
Mixed Crystals ◽  
Optical Absorption Spectra ◽  
Optical Studies ◽  
Excitation Spectra ◽  
X Ray ◽  
Wavelength Side

Optical absorption spectra of KBr:Tl+(0.0125 mol%) single crystals shows A, B and C bands around 258, 220 and 210 nm respectively. In KCl0.1Br0.9:Tl+(0.0125 mol%) mixed crystals exhibit slightly broadening of the A-band towards lower wavelength side. The broadening of the absorption spectra are suggested to be due to some complex Tl+centers involving Br-and Cl-ions formed in the mixed crystals. When excited at A, B and C-bands of Tl+ions, PL of KBr:Tl+showed emission band around 320 with a prominent shoulder around 365 nm. In KCl0.1Br0.9mixed crystals the shoulder around 365 nm is not prominent due to the perturbing influence of Cl-ions. Addition bands in the excitation spectra are attributed to the presence of Tl+dimmers. PSL observed in X-ray irradiated crystals resembled their respective PL emissions indicating that PSL in them is due to Tl+ions.

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