Short Note
The Study of Short-Lived Nuclei in the Region Z= 59-68
G.D. Alkhazov, K.A. Mezilev, and Yu.N. Novikov
Leningrad Nuclear Physics Institute, Leningrad, USSR
N. Ganbaatar, K.Ya. Gromov, V.G. Kalinnikov, A. Potempa, E. Sieniawski,
and F. Tarkanyi
Joint Institute for Nuclear Research, Head Post Office, P.O. Box
79, 101000 Moscow, USSR
Received January 19, 1983
Abstract
b+ -ray endpoint energies for mass-separated
samples of neutron deficient Rare-Earth isotopes have been measured using
an intrinsic germanium detector. Q EC values have
been obtained and new isomeric states have been identified for the first
time.
Knowledge of accurate atomic masses is both of fundamental and practical
importance. Mass determination for nuclides far from the stability line
requires mass differences derived from b -endpoint
measurements.
At the IRIS on-line mass-separator facility [1] using Ge(HP) technique
systematic investigation of b + -endpoint energies
were undertaken for neutron deficient RE isotopes.
The nuclei were produced in spallation reaction on Ta target with 1
GeV proton beam from synchrocyclotron. The b
+, g , X spectra of mass separated samples were
recorded parallely using Ge(HP) and Ge(Li) detectors, which allowed to
analyse the isotopic composition of the isobars in the samples and to check
possible contamination of other (A ± 1, A-16)
masses. For isotopic identification of the components of b
+ spectra the decay characteristics (time dynamic) of the spectrum were
followed. The details of sample production, measurement techniques, identification
principles and data analysis were very similar to those employed in our
previous studies [2]. The principles of data analysis of continous positron
spectra will be published elsewhere.
The experimental b + -endpoint energy values
and the derived total decay energies Q EC are summarized in
Table 1.
The Q EC values for 138mPm , 146mTb
and 147mDy isomers are based on the following new experimental
results [3] :
- Via b + and X , g
measurements a new long-lived isomeric state has been identified in 138Pm
(T 1/2 = 10 ± 2 s).
- Our experimental results from b + and
conversion electron studies on A=146 isobar confirm the results of Munchen
group [4] concerning the half-life and spin-parity assignments of 146mTb
(1+) isomer.
From our investigation of the decay scheme of 147m+g Dy isomers, the half-life of 147Dy ground state (T 1/2 = 75 ± 4 s, Ip = 1/2 ) and the sequence of low lying levels of 147Tb have been found: 0 keV (11/2- g.s.), 50 keV (1/2+), 303 keV (3/2+), 404 keV (5/2+), 769 keV (7/2+).
The analysis of the data is in progress, and more complete results will be published.
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REFERENCES
1. E.Ye.Berlovich et al., Proc. 8th Int.EMIS Conf. Skovde, Sweden, 1973, p.349.
2. E.Ye.Berlovich et al., Acta Phys.Polonica, Bl1, 1980, p. 455.
3. G.D. Alkhazov et al., Proc. of 9th EPS Nuclear Physic Division Conference, Amsterdam, 1982, v.1, p.264.
4. E.Nolte et al., Z.Phys., A306, 1982, p. 223.