TRIAC Progress Report - KEK

as shown in Fig. 3-36 (a) and (b), respectively. These spectra include the prompt time
components from Compton events caused by higher-energy γ rays. The lifetimes were
deduced by fitting an exponential decay curve, a exp(-t/τ)+b , by a least-χ 2 method.
Contributions of lifetimes of higher-lying states are neglected because their lifetimes are
expected to be much shorter than that of the 2 + states. The lifetimes were determined to
be 3.98(8) ns and 4.0(2) ns, for 162, 164 Ga, respectively. Here, the errors were estimated
from the spread of various fitted values obtained by changing the fitting range. In
addition to these nuclei, the lifetime of the 2 + state in 160 Ga was also measured from β
delayed γ rays from 140 Eu. The resultant lifetime was 3.94(12) ns, which was in good
agreement with the previous result of 3.91(8) ns, well verifying the present experiment.
The measured lifetime were converted to B (E2;0 + 2 + ) values by taking into
account the total internal conversion coefficients αT taken from the ICC code in the
program [3-52], and the energies of the first 2 + state. The obtained B (E2;0 + 2 + )
values were deduced to be 5.45(11) e 2 b 2 and 5.2(3) e 2 b 2 for 162,164 Gd, respectively.
Fig. 3-36. Time interval spectra between β rays and γ rays from the fist 2 + state in 162 Gd (a) and
164 Gd (b), respectively [3-52]. The results of the fitting were demonstrated by the solid lines. See
the text for the details.
3-4-3. Time differential perturbed angular correlation in highly oriented pyrolytic
graphite (K06)
When a radioactive nucleus with a large quadrupole moment is implanted into a
material, the emission of radiation is affected by the (neighboring) magnetic field and/or
an electric field gradient at the implanted place. In addition, if the radionuclide emits
two gamma rays in cascade via an intermediate state whose lifetime is in order of ns, the
emission pattern reflects the dynamics of the internal material. In other words, we can
deduce the nano-scale structure concerning the extranuclear charge distribution, and
magnetic properties of the material by measuring the angular correlation between the
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