Primary versus secondary $\mathit{\gamma }$ intensities in ${}^{171}\mathrm{Yb}$$(n_{\mathrm{th}},\gamma )$

The two published literature values [Greenwood et al., Nucl. Phys. A252, 260 (1975) and Gelletly et al., J. Phys. G 11, 1055 (1985)] for absolute primary γ intensities following thermal neutron capture of ${}^{171}\mathrm{Yb}$ differ on average by a factor of 3. We have resolved this conflict in favor of Greenwood et al. by a measurement of primary versus secondary intensities.

Figure 1

Efficiency calibration of the three Ge detectors using some 20 lines from the ${}^{35}\mathrm{Cl}$$(n,\gamma )$${}^{36}\mathrm{Cl}$ reaction. Solid and open symbols correspond to NaCl and ${\text{AlCl}}_3$ salts, and diagonal and parallel target-mounting options, respectively (see text). For the purpose of the figure, the efficiency is brought roughly to an absolute scale using a calibrated ${}^{60}\mathrm{Co}$ source, but the two runs are displaced by 10% up or down for better visibility. The efficiency is fitted on a logarithmic plot by a second-order polynomial (solid lines). The dotted lines correspond to a 5% error band estimated from the spreading of the data points.

Figure 2

Normalized yields of secondary (left panels) and primary (right panels) γ rays. The error bars are because of uncertainties in the relative intensities and peak areas only. The lines show average values of the normalized yields (solid lines), their error bands including an overall 5% systematic uncertainty because of the efficiency calibration (dashed lines), and the spread of data points (dotted lines). Upper and lower panels correspond to diagonal and parallel mounts of the target ampules, respectively, and different chlorine salts used for the efficiency calibration (see text).