ARAGONITE TO CALCITE TRANSFORMATION STUDIES BY ESR OF Mn2+ IONS IN SINOTAIA INGALLSIANA

2009 ◽  
Vol 23 (09) ◽  
pp. 1243-1247
Author(s):  
NITINAI UDOMKAN ◽  
PICHET LIMSUWAN
Keyword(s):  
Hyperfine Coupling ◽  
Fine Powder ◽  
Hyperfine Coupling Constant ◽  
Freshwater Snail ◽  
Zero Field ◽  
Coupling Constant ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Air Atmosphere ◽  
Biomineralization Process

We have studied paramagnetic Mn 2+ ions present in the freshwater snail, Sinotaia ingallsiana (FS), Viviparus which are abundant in Thailand. The FS shells in our study were ground into fine powder. A set of seven samples was each then separately annealed for 2 hours in air atmosphere at 300°C, 400°C, 500°C, 600°C, 700°C, 800°C and 900°C, respectively. Our detailed ESR spectral analyses of FS show that Mn 2+ ions enter Ca 2+ sites during a biomineralization process. The hyperfine coupling constant (A) and zero-field splitting (D) in the ESR spectrum of Mn 2+ in calcite and aragonite were determined. The spreading of the non-central allowed transitions was analyzed and the experimental transitions were attributed. For calculating the hyperfine coupling constant, five methods for calculating the zero-field splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from 87.50 to 89.00 G and those of the zero-field splitting range from 110.00 to 116.00 G.

scholarly journals The Coordination Chemistry of Phosphoryl Compounds Containing the -N(CH3)2 Group, XII.

1973 ◽  
Vol 28 (3-4) ◽  
pp. 104-106 ◽  
Author(s):  
M.W.G. De Bolster ◽  
B. Nieuwenhuijse ◽  
J. Reedijk
Keyword(s):  
Electron Spin Resonance ◽  
Metal Ion ◽  
Room Temperature ◽  
Esr Spectroscopy ◽  
Hyperfine Coupling ◽  
Hyperfine Coupling Constant ◽  
Zero Field ◽  
Coupling Constant ◽  
Spin Resonance ◽  
Temperature Electron

Room temperature electron spin resonance powder spectra have been recorded for some compounds of the type Mn(ligand)p(anion)2 with hexamethylphosphoramide and nonamethylimidodiphosphoramide as ligands (p = 1 - 4) and BF-4, NO-3, Cl-, Br-, I- and NCS-as anions.The values for the zero-field parameters, D and λ, have been determined and are compared with literature data. It is shown that ESR spectroscopy can be very helpful in elucidating the structures of manganese(II) complexes.The high values for the hyperfine coupling constant of the solvates suggest that in these complexes the bonding between the ligands and the metal ion is essentially ionic.

ELECTRON SPIN RESONANCE STUDIES OF Mn2+ IN FRESHWATER SNAIL SHELLS: S. INGALLSIANA, P. AMPULLACEA, P. CANALICULATA LAMARCK AND FOSSILIZED SNAIL SHELL

2004 ◽  
Vol 18 (26) ◽  
pp. 3419-3428
Author(s):  
S. MEEJOO ◽  
N. UDOMKAN ◽  
P. WINOTAI ◽  
Y. CHAIMANEE
Keyword(s):  
Fine Powder ◽  
Freshwater Snail ◽  
Esr Spectra ◽  
Pomacea Canaliculata ◽  
Air Atmosphere ◽  
Biomineralization Process ◽  
Spin Resonance ◽  
Powder Samples ◽  
Irreversible Phase Transformation ◽  
A Minor

We have studied paramagnetic Mn 2+ ions present in the shells of today's univalve freshwater snails, Sinotaia ingallsiana (FS), Pila ampullaceal (PA), Pomacea canaliculata lamarck (PCL) and the fossilized freshwater snail (FFS), Viviparus which are abundant in Thailand. The FS, PA and AG shells in our study were ground into fine powder. A set of seven samples was each then separately annealed for 2 hours in air atmosphere at 300°C, 400°C, 450°C, 500°C, 550°C, 600°C and 900°C, respectively, while the FFS powder was characterized as received. The FS, PA and PCL shells mainly consist of aragonite and a fraction of calcite. The heat treatments higher than 450°C of the FS, PA and PCL powder samples resulted in an irreversible phase transformation from aragonite to calcite. However, it is found that the FFS shell is mainly made of calcite, with a minor fraction of aragonite. The crystal structure of high temperature annealed FS, PA and PCL samples are quite similar to that of FFS, which indicates that the metamorphosis (aragonite → calcite) in the FFS shell had occurred but not yet completed, although they remained under the pressure and temperature of the Earth's crust over millions of years. Our detailed ESR spectral analyses of FS, PA, PCL and FFS show that Mn 2+ ions enter Ca 2+ sites during a biomineralization process. Typical simulated ESR parameters of FS-500 of Mn 2+ at a uniaxial site of calcite are gx=gy=2.078±0.001, gz=2.002±0.001, Ax=Ay=87.50±1.00 G , Az=89.00±1.00 G and D=115±1 G , respectively. It is surprising to find that the ratio of Mn 2+ concentration present in FFS to those in FS, PA and PCL shells evaluated from ESR spectra is as much as 10:1. It is thus possible to gain some insight of manganese incorporation into the freshwater shells during the biomineralization process.

Correlating the axial Zero Field Splitting with the slow magnetic relaxation in GdIII SIMs

2021 ◽  
Author(s):  
Júlia Mayans ◽  
Albert Escuer
Keyword(s):  
Magnetic Relaxation ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Field Splitting ◽  
Slow Magnetic Relaxation

A possible relation between the value of the axial Zero Field Splitting and the occurrence of field-induced slow magnetic relaxation has been established for a new gadolinium(iii) compound.

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