Conversion Coefficient Measurements Research Articles

Internal Conversion Coefficients ofγRays inPu239

The $K$-conversion coefficients of the predominantly $M1$ $\ensuremath{\gamma}$ rays of 209.7, 228.2, and 277.9 kev following the $\ensuremath{\beta}$ decay of ${\mathrm{Np}}^{239}$ have been measured using a curved crystal $\ensuremath{\gamma}$-ray spectrometer and a lens type $\ensuremath{\beta}$-ray spectrometer. The measured $K$-conversion coefficients are 1.76\ifmmode\pm\else\textpm\fi{}0.30, 1.60\ifmmode\pm\else\textpm\fi{}0.16, and 1.16\ifmmode\pm\else\textpm\fi{}0.12, respectively. A limit of less than 10% has been placed on the admixture of $E2$ in these radiations from a study of the $\frac{K}{L}$ and ${L}_{\mathrm{I}}:{L}_{\mathrm{II}}:{L}_{\mathrm{III}}$ conversion ratios. It is found, for $Z=94$, that the measured conversion coefficients show better agreement with the $M1$ predictions of Sliv who allowed for finite nuclear size than with Rose et al. who assumed a point charge nucleus. In addition, the $K$-conversion coefficients of the 254.7-, 285.5-, 316.2-, and 334.4-kev $\ensuremath{\gamma}$ rays of ${\mathrm{Pu}}^{23}$, have been measured to be 0.88\ifmmode\pm\else\textpm\fi{}0.32, 0.11\ifmmode\pm\else\textpm\fi{}0.02, 0.027\ifmmode\pm\else\textpm\fi{}0.005, and 0.025\ifmmode\pm\else\textpm\fi{}0.005, and the ${L}_{\mathrm{I}}$ and ${L}_{\mathrm{II}}$ conversion coefficients of the 106.4-kev $\ensuremath{\gamma}$ ray to be 0.062\ifmmode\pm\else\textpm\fi{}0.007 and 0.071\ifmmode\pm\else\textpm\fi{}0.007, respectively.

Decay ofHf181

The decay of ${\mathrm{Hf}}^{181}$ to ${\mathrm{Ta}}^{181}$ was studied by angular correlation measurements ($133K\ensuremath{-}482\ensuremath{\gamma}$, $133\ensuremath{\gamma}\ensuremath{-}482\ensuremath{\gamma}$, and $133\ensuremath{\gamma}\ensuremath{-}482K$, energies being given in kev), conversion coefficient measurements [${\ensuremath{\alpha}}_{K}(133)=0.50\ifmmode\pm\else\textpm\fi{}0.06$, ${\ensuremath{\alpha}}_{K}(136)=1.2\ifmmode\pm\else\textpm\fi{}0.2$, ${\ensuremath{\alpha}}_{K}(346)=0.038\ifmmode\pm\else\textpm\fi{}0.007$, ${\ensuremath{\alpha}}_{K}(482)=0.023\ifmmode\pm\else\textpm\fi{}0.002$], $\frac{K}{L}$ ratios, and coincidence measurements. The weak 137-kev transition, first observed by Mihelich, was placed in the decay by delayed coincidence measurements. The spin assignments are in excellent agreement with the calculations of Nilsson on the strong-coupling model. Comparison of $K\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ correlation coefficients in the Hf${\mathrm{O}}_{2}$ sources fails to show any after effects of $K$-hole formation on the correlation coefficients. The discrepancy between the $\frac{E2}{M1}$ ratio obtained from $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ correlation measurements and conversion coefficient measurements in the 482-kev transition is discussed in terms of the improved finite nuclear size corrections to $M1$ conversion coefficients described by Church and Weneser.

On the decay of 48Sc and 48V

Synopsis The spin assignments of the known levels in 48 Ti excited in the decay of 48 Sc and 48 V have been checked by angular correlation and conversion coefficient measurements. The spin and parity of the 3.24 MeV level were uniquely determined as 4+. The γ -ray energies were found to be 986 ± 3 ( γ 1), 1040 ± 3 ( γ 2), 1314 ± 4 ( γ 3) and 2253 ± 15 ( γ 4) keV, the end points of the negaton and positon spectra in 48 Sc and 48 V 654 ± 7 and 698 ± 4 keV and the decay energies of these nuclides 3994 ± 9 and 4020 ± 7 keV respectively. The intensity of a possible 940 keV γ -ray suggested by earlier coincidence measurements is found to be smaller than 5%. Positon decay occurs in (55.6 ± 0.8) % of the 48 V transitions; this value is in agreement with theoretical predictions by Zweifel if no 940 keV γ -ray occurs. The half-life of 48 V was measured as 16.15 ± 0.17 days.

Nuclear Energy Levels ofTl203

Using scintillation spectrometry and coincidence counting techniques, ${\mathrm{Tl}}^{203}$, formed by orbital electron capture in ${\mathrm{Pb}}^{203}$, has been shown to emit gamma rays of energies 280, 403, and 683 kev. The 403- and 280-kev gamma rays were found to be in sequence; the 683-kev gamma ray represents the associated cross-over transition. By energy and conversion coefficient measurements, it has been shown that the same 280\ifmmode\pm\else\textpm\fi{}2 kev level of ${\mathrm{Tl}}^{203}$ is excited in the decay of both ${\mathrm{Hg}}^{203}$ and ${\mathrm{Pb}}^{203}$. A coincidence method for the measurement of the conversion coefficients of the 403-kev gamma rays is described. The $K$-shell conversion coefficient of the 403-kev gamma ray has been measured as 0.076, the $\frac{K}{(L+M)}$ ratio being 3.7. The angular correlation function for the 403-kev---280-kev cascade has the form $W(\ensuremath{\theta})=1\ensuremath{-}(0.152\ifmmode\pm\else\textpm\fi{}0.007){cos}^{2}\ensuremath{\theta}$. For the known multipole mixture of the 280-kev quantum, the correlation measurements indicate the 403-kev transition to be 76 percent $E2$ and 24 percent $M1$. The interference phases of the $E2$ and $M1$ matrices of both transitions are the same in Lloyd's notation. The angular correlation studies and the conversion coefficient measurements indicate the orbitals of the levels of ${\mathrm{Tl}}^{203}$ to be ${d}_{\frac{5}{2}}$, ${d}_{\frac{3}{2}}$, and ${s}_{\frac{1}{2}}$, in order of decreasing excitation energy. The spin of the ground state of ${\mathrm{Pb}}^{203}$ is shown to be $\frac{5}{2}(\ensuremath{-})$.

K-Conversion Electron-Gamma Angular Correlation Measurements inTe121andTe123

This note describes preliminary measurements of K-conversion electron-gamma correlation measurements in the two-step isomers, Te/sup 121/ and Te/sup 123/. In order to separate unambiguously the K and L correlations, a lens spectrometer has been employed for electron detection. To date, theoretical correlation coefficents are only available for the K shell. The isomers studied are of interest since conversion coefficient measurements indicate the second transition is predominately magnetic dipole, whereas shell model assignments would forbid ordinary M1 transitions. Partial breakdown of this selection rule would yield depressed M1 transition probabilities and might allow competition by the slower electric quadrupole transition.

Measurement of Some Internal Conversion Coefficients

Measurement of Some Internal Conversion Coefficients