Properties of the 319-keV Excited State ofPd105

Abstract

Using the high peripheral velocities of an ultracentrifuge as the means of compensating for the recoil energy losses, resonance scattering from the 319-keV level in ${\mathrm{Pd}}^{105}$ has been observed with a ${\mathrm{Rh}}^{105}$ source. From the magnitude of the scattering effect, a mean life ${\tau }_{\gamma }=(2I+1)(0.91\mathrm{}\pm 0.05)\times {10}^{-11\mathrm{}}$ sec, $I$ being the spin of the excited state, was obtained for the ground-state transition which is a mixture of $M1\mathrm{}$ and $E2\mathrm{}$. The angular distribution of the resonance radiation was found to be of the form $W\left(\theta \right)=1+(0.25\mathrm{}\pm 0.03)P_2\left(cos\theta \right)$; this eliminated the value ½ for the spin of the excited state. Combining the measured mean life with the $B\left(E2\mathrm{}\right)\mathrm{}$ from Coulomb excitation, the absolute value of the mixing amplitude $\delta$ may be restricted to $\left|\delta \right|={{0.14}_{-0.02\mathrm{}}}^{+0.03\mathrm{}}$. The experimentally observed angular distribution and this value of $\left|\delta \right|$ cannot be accounted for if a spin of $\frac{3}{2}$ is assigned to the 319-keV level. Of the two remaining spin values, $\frac{5}{2}$ and $\frac{7}{2}$, spin $\frac{7}{2}$ is favored by the experimental evidence.