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تسجيل مستخدم جديدPrecise measurement of alpha-K for the 65.7-keV M4 transition in 119Sn: Extended test of internal-conversion theory
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We have measured the K-shell internal conversion coefficient, alpha-K, for the 65.7-keV M4 transition in 119Sn to be 1621(25). This result agrees well with Dirac-Fock calculations in which the effect of the K-shell atomic vacancy is accounted for, and disagrees with calculations in which the vacancy is ignored. This extends our precision tests of theory to Z = 50, the lowest Z yet measured.
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We have measured the K-shell and total internal conversion coefficients (ICCs), alpha_K and alpha_T, for the 109.3-keV M4 transition in 125Te to be 185.0(40) and 350.0(38), respectively. Previously this transitions ICCs were considered anomalous, wit
h alpha values lying below calculated values. When compared with Dirac-Fock calculations, our new results show good agreement. The alpha_K result agrees well with the version of the theory that takes account of the K-shell atomic vacancy and disagrees with the one that does not. This is consistent with our conclusion drawn from a series of high multipolarity transitions.
We have measured the K-shell internal conversion coefficient, alpha_K, for the 88.2-keV M4 transition from the 106-day isomer to the ground state in 127Te to be 484(6). When compared with Dirac-Fock calculations of alpha_K, this result agrees well wi
th the version of the theory that incorporates the effect of the K-shell atomic vacancy and disagrees with the one that does not. As a byproduct of this measurement, we have determined the beta branching from the isomer to be 2.14(3)%.
We have measured the K-shell and total internal conversion coefficients, alpha_K and alpha_T, for the 150.8-keV E3 transition in 111Cd to be 1.449(18) and 2.217(26) respectively. The alpha_K result agrees well with Dirac-Fock calculations in which th
e effect of the K-shell atomic vacancy is accounted for; it extends our precision tests of alpha_K calculations to Z = 48, the lowest Z yet measured. However, the result for alpha_T disagrees by about two standard deviations from the calculated alpha_T value, whether or not the atomic vacancy is included.
Neutron-activated sources of $^{103}$Ru and $^{103}$Pd both share the isomeric first-excited state in $^{103}$Rh as a daughter product. From independent measurements of both decays, we have measured the $K$-shell and total internal conversion coeffic
ients, $alpha_K$ and $alpha_T$, for the 39.8-keV $E$3 transition, which de-excites that state in $^{103}$Rh, to be 141.1(23) and 1428(13), respectively. When compared with Dirac-Fock calculations, our new results disagree with the version of the theory that ignores the $K$-shell atomic vacancy, which is consistent with our conclusion drawn from a series of measurements on high multipolarity transitions in nuclei with higher $Z$. Calculations that include the atomic vacancy indicate that the transition actually has a small $M$4 component with mixing ratio $delta$ = 0.023(5).
We have been testing the theory used to calculate internal-conversion coefficients (ICCs) by making a series of measurements of alpha_K values with precision better than +/-2%. So far we have measured E3 transitions in three nuclei, 103Rh, 111Cd and
134Cs; and M4 transitions in six nuclei, 119Sn, 125Te, 127Te, 137Ba, 193Ir and 197Pt. Together, these span a wide range of A and Z values. In all cases, the results strongly favor Dirac-Fock calculations in which the final-state electron wave function has been computed in an atomic field that includes the vacancy created by the internal-conversion process.
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