Étude de la capture radiative des neutrons de résonance dans le platine

Résumé

The statistical properties of the partial radiation widths in ¹⁹⁶Pt have been studied with the Saclay linear accelerator using the time-of-flight method and a Ge(Li) detector. The spectra for 22 resonances with spin and parity 1⁻ were analysed, and a sample of 66 transitions was obtained. The result of such a study confirms the validity of the Porter-Thomas distribution for these widths; the data agree with a _χ²-distribution with one degree of freedom and are clearly inconsistent with the exponential law. Several statistical analysis methods have been used. From the number of 1⁻ resonances, it is possible to calculate the average relative intensity of some transitions and to compare them with values calculated from theoretical estimates.

In addition a new level scheme of doubly even ¹⁹⁶Pt nuclei has been obtained and is compared with previous results and theoretical predictions; 40 levels have been found. This scheme is confirmed by thermal neutron capture and by ¹⁹⁶Au radioactive decay. A partial scheme is obtained for some odd isotopes of platinum (¹⁹³Pt, ¹⁹⁷Pt and ¹⁹⁹Pt).