Precise atomic masses of147Eu,147Gd, and151Tb derived from their decay properties

Abstract

The fl-decay energies of '4VEu, 147Gd, and ~5~Tb were determined by using 7-spectroscopical methods. The comparison of experimental with calculated K-capture probabilities yielded the QEc values 1.690(+_2~)MeV and 2.203C1~)MeV for ~47Eu and ~47Gd, respectively. By measuring the ratio of positron decay to electron capture for two branches in ~4VEu decay, the decay energies QEC=1'702(13) MeV and QEC =l.709(18) MeV were derived. Also from EC/fl + ratios the values QEC=2.225(75) MeV for 147Gd, and QEc=2.566(12)MeV for 15aTb were obtained. Earlier discrepancies in the mass adjustment of these isotopes were removed. In course of the present studies 7-decay properties of ~47Eu and a4VGd were reinvestigated.

Measurement of the147Gd mass excess by the (12C,9Be) reaction

“…3. It is situated inbetween the previous values, being close to the results of the decay study [8] and the one-neutron pick-up reactions [9], and deviating by 89_+55 keV from the result of the previous study [6b] of the same reaction. Compared to the earlier work [6b], the present one took advantage of 1) the knowledge of the mass of 146Gd, 2) the realization of three independent measurements with improved statistics,…”

“…However, a discrepancy still exists between the results concerning the 147Gd mass excess as can be seen from Table 1. The first quoted value was obtained from the reaction 144Sm(12C, 9Be)l*TGd [6b], the second one comes from 147Gd ]~-decay studies [8], and the third results from the 14aGd(p,d), (d,t) and (~,e) reaction studies [9]. The two latter results are seen to agree well with one another.…”

“…It should be mentioned that the results of [8] and [9] are relying upon the mass excess of 147Eu, and 148Gd, respectively, which are each known with a 4 keV-accuracy [13], while our result, and to a lesser extent the result from [6b], are linked to the 146Gd mass. Concerning the 146Gd mass excess, we have averaged the accurate results of the reaction studies [6a-c], but preferred not to include the upper and lower limits of the 146Gd Q~ value [6d], since the latter measurement is providing only an energy window of 100keV.…”

Atomic masses of147m, 148m, 149m Tb,148Dy,150m, 152m Ho derived from decay properties

“…In the present communication we report on Q~c measurements of 147m, 148m, 149rnTb ' 148Dy and 15~ continuing our earlier work of mass 9 measurements by y-spectroscopic techniques [5][6][7].…”

“…In particular, the nuclei 147m'148m'149myb and as~ are connected by Q~c-and Q~-values to 144Sm, 145Sm, 14SEu, 146Gd and 147Gd. The masses of these nuclei are well known: 144Sm [9,35] is stable, the masses of 145Sm [10], 145Eu [5] and 147Gd [6] were redetermined in our earlier investigations, and accurate mass values for 146Gd were recently derived independently by reaction studies [11][12][13].…”