Experimental beta-decay energies of several neutron-rich nuclides with mass number 131?A?146

Abstract

With sources obtained from the on-line mass separator LOHENGRIN the beta-decay energies of 13~Sn, 134Sb, 135'~36Te, ~'3'146Ba and 146La have been determined from measured fl-endpoint energies. The experimental values are compared with the predictions of several mass formulae.

Beta-decay energies of neutron-rich nuclei in the mass region 142?A?150

“…From the /~-endpoint energies given in Table 1, a consistent Q~-valuc of 6,620+ 70 keV is obtained for the 6.2s isomer of 146La. This value agrees within errors with the Qa-value reported in our earlier study [6]; but there, this value was attributed to the 10 s isomer. The decay energy of this isomer must be considered as uncertain; it is planned to study its decay again in the near future at the LOHENGRIN mass separator.…”

“…The main aim of the present study was the search for nuclear structure effects in the mass region A~150. Therefore, in addition to the new Q~-measurements described above, some /?-decay energies obtained in earlier studies [5,6,8] have been re-evaluated. In this new evaluation, an improved data handling procedure to decompose the complex /?-spectra and to subtract the background was applied, which had been developed in the meantime [11].…”

“…Based upon the decay schemes of these authors, two Q~-values for 146La have been proposed by us earlier [6], which were obtained in experiments at the LOHENGRIN mass separator, where the nuclide t46La is directly produced. In the meantime, no other study of the isomerism in 146La has been reported.…”

Levels of146Ce studied through the decay of high-spin isomer of146La

“…The sum of the placed y-ray intensities (including intensities of the tentatively placed lines) amounts to 97% of the total y-ray intensity. Using the 7-ray intensities corrected for internal conversion and the Qp-value of 6660 __+ 120 keV [ 11 ], we have calculated the B-feedings and log ft values [20] for all excited levels. In this calculation, the B-feedings to the ground state of 146Ce and to levels with spin values of 2 or less were assumed to be zero.…”

“…The isomerism in 146La was first reported by Monnand et al [10] who measured the half-lives of the low-and high-spin isomers to be 6.2 and 10.0 s, respectively. Keyser et al [ 11 ] measured the Q~-values for the two isomers of ~46La at the mass separator LOHENGRIN and reported that the high-spin isomer was the ground state of 146La, although this assignment was not confirmed by the results of later Q~-value measurements [12][13][14]. The decay of the low-spin 2-isomer of 146La with T~/2= 6.27 s has been investigated at the mass separator TRISTAN, where this isomer is predominantly produced through the /?…”