Coulomb Excitation of the Second 2+ States in W, Os, and Pt Nuclei

Abstract

The location of a second 2+ state is established for six -even-even nuclei by means of Coulomb excitation produced by 4 to 5 Mev protons. The relatively weak excitation of these states is detected by a measurement of the gammaray yields from singles spectra and from coincident measurements of the cascade gamma rays. The B(E2)'s for decay of the second 2+ state to ground state by the crossover transition exhibit some uniformity for the even-even isotopes of W and Os, being about 6 times the single-particle value. The cascade/crossover ratio for the decay of the second 2+ state is known for these nuclei. The upper cascade B(E2)'s exhibit enhancements of 10 to 60 times the single-particle value. The ratios of the B(E2)'s for decay of the first and second 2+ states are compared to the predictions of several collective models. For five of these nuclei the E2/M1 ratio is known for the upper cascade transition. The B(M1) values obtained are exceedingly small compared to the single-particle estimate. This result is in qualitative agreement with the collective models which predict that M1 radiation is forbidden in the decay of vibrational excitations. (auth)