With ${\mathrm{Sn}}^{119m}$ sources in two different chemical forms, high-resolution internal-conversion measurements were made of electron lines from the 23.87-keV $M1\mathrm{}$ transition. It was found that the $5s$ (valence-shell) electron density near the nucleus is about 30% smaller in Sn${\mathrm{O}}_2$ than in white tin; calculations show that roughly 17% of this decrease in $5s$ electron density is compensated for by an increase in the sum of $1s$, $2s$, $3s$, and $4s$ densities. With this information on $s$ electron densities and from the value of the Mössbauer chemical isomer shift between white tin and Sn${\mathrm{O}}_2$, it has been possible to conclude that the nuclear charge radius of the 23.87-keV state of ${\mathrm{Sn}}^{119}$ is 3.3×${10}^{-4\mathrm{}}$ larger than that of the ground state.

• Received 1 September 1966

DOI:https://doi.org/10.1103/PhysRevLett.17.809