The 79-kev transition in ${\mathrm{Cs}}^{133}$, which is known to be $l$-forbidden ($\Delta l=2\mathrm{}$) magnetic dipole ($M1\mathrm{}$), has been analyzed for penetration effects suggested by Church and Weneser. A value of 6.5±2.6 is found for $\lambda$, the ratio of the matrix element due to penetration of the atomic electron into the nucleus and the matrix element due to $M1\mathrm{}$ gamma emission. This value of $\lambda$ is to be compared with the range 5-10 obtained by Church and Weneser for $l$-forbidden ($\Delta l=2\mathrm{}$) transitions using empirical gamma matrix elements and single-particle wave functions to evaluate the electron matrix element.

• Received 20 April 1960

DOI:https://doi.org/10.1103/PhysRev.119.2021