The total internal-conversion coefficients have been measured for $E2\mathrm{}$ transitions from first excited state to ground state in five heavy deformed nuclei. $\alpha$-particle gating was used to determine the population of the first excited levels from parent decays. Photon spectra, as observed by a well-type NaI(Tl) detector in coincidence with the gating $\alpha$ particles, were analyzed to determine the ratio of $\gamma$ transitions to total transitions. The $\alpha$ gating spectra and photon spectra were analyzed on a computer, when necessary, using a nonlinear least-squares curve-fitting program. The resulting coefficients are 19.6±1.4 for the 84.4-keV transition in ${\mathrm{Ra}}^{224}$, 158±7 for the 57.6-keV transition in ${\mathrm{Th}}^{228}$, 780±55 for the 43.5-keV transition in ${\mathrm{U}}^{234}$, 607±29 for the 45.28-keV transition in ${\mathrm{U}}^{236}$, and 845±93 for the 42.88-keV transition in ${\mathrm{Pu}}^{240}$. The internal-conversion coefficient for the transition in ${\mathrm{Pu}}^{240}$ is somewhat lower than the theoretical predictions of Hager and Seltzer and of Sliv and Band, whereas the internal-conversion coefficient for the transition in ${\mathrm{U}}^{234}$ is somewhat higher. The internal-conversion coefficients for the remaining transitions agree with the theoretical values within the experimental uncertainties.

• Received 7 March 1968

DOI:https://doi.org/10.1103/PhysRev.173.1125