The isotope ratios of cerium and lanthanum are determined precisely by a surface ionization mass spectrometer.
138Ce/
142Ce and
140Ce/
142Ce ratios for Ce standard solution are 0.0225762± 0.0000014 (2
σ) and 7.9471±0.0003 (2
σ), normalized to
136Ce/
142Ce=0.01688, respectively.
138La/
139La ratio is 0.0009025±0.0000005 (2
σ). The oxygen isotope ratios in measurements of REE as oxide ions are 0.0003916±0.0000014 (2
σ) and 0.002129±0.000010 (2
σ) for
17O/
16O and
18O/
16O. The isotopic abundances (%) of
136Ce,
138Ce,
140Ce and
142Ce are calculated to be 0.1878, 0.2512, 88.433 and 11.128, respectively. The isotopic abundances (%) of
138La and
139La are calculated to be 0.09016 and 99.9098. These isotopic abundances obtained here give the following relation:
(
138La/
142Ce)
ATOMIC=0.008173×(La/Ce)
WEIGHT.
These precise isotopic abundances on Ce and La are fundamental values in a La-Ce geochronometer.
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