Isotopic variations of Sm, Gd, Er and Yb found in planetary materials caused by neutron-capture reactions in nature

Journal of Analytical Science and Technology

Table 3 The results of calculated ¹⁶⁸Yb/¹⁷⁴Yb and ¹⁷⁰Yb/¹⁷⁴Yb isotopic ratios from the estimated neutron fluences (Ψ:10²⁰ n cm⁻²) and calculated neutron fluences from the measured Yb isotopic ratios for nine of the Oklo natural reactor materials

Sample	Referred^a		Calculated^b		Measured^a		Calculated^c
Sample	Ψ_th	Ψ_epi	¹⁶⁸Yb/¹⁷⁴Yb	¹⁷⁰Yb/¹⁷⁴Yb	¹⁶⁸Yb/¹⁷⁴Yb	¹⁷⁰Yb/¹⁷⁴Yb	Ψ_th	Ψ_epi
STD	0	0	0.003956	0.094801	0.003956	0.094801	0	0
SC55-1852	1.18	0.066	0.002944	0.102858	0.002056	0.111322	2.47	0.21
KN267-2194	4.02	0.347	0.001386	0.123073	< 0.001	0.180793	NA	NA
KN245-2674	1.91	0.100	0.002461	0.107669	0.001489	0.120051	2.99	0.73
KN250-2682	1.05	0.045	0.003056	0.101829	0.002731	0.105047	1.28	0.21
SF84-1469	4.87	0.380	0.001128	0.128416	< 0.001	0.183674	NA	NA
SF84-1480	7.62	0.364	0.000603	0.144095	< 0.001	0.204620	NA	NA
SF84-1485	5.87	0.354	0.000905	0.133937	< 0.001	0.177657	NA	NA
SF84-1492	5.29	0.353	0.001035	0.130561	< 0.001	0.183774	NA	NA
SD37	7.06	0.736	0.000600	0.144886	< 0.001	0.245122	NA	NA

STD means a standard reference materials of Yb
Ψ_th and Ψ_epi are expressed in 10²⁰ (n cm⁻²) unit
^aThe data for the estimated Ψ_th and Ψ_epi, and measured isotopic ratios of ¹⁶⁸Yb/¹⁷⁴Yb and ¹⁷⁰Yb/¹⁷⁴Yb are given by Holliger and Devillers (1981) and Hidaka and Holliger (1998)
^bThe isotopic ratios were calculated by substituting the estimated Ψ_th and Ψ_epi into Eqs. (6) and (7)
^cThe neutron fluences were calculated by substituting the measured ¹⁶⁸Yb/¹⁷⁴Yb and ¹⁷⁰Yb/¹⁷⁴Yb isotopic ratios into Eqs. (6) and (7)