Corrections to the nuclear lifetime value for the 1314-keV level of 144 Nd

No Thumbnail Available
Wunker, Charles T.
Issue Date
Thesis (M.A.)
Other Identifiers

In an earlier study performed by Jack Collins at the Ball State University Nuclear Spectroscopy Laboratory, measurements were made of the nuclear half-lifetime for the 1314- and 696-keV levels of 144Nd. That study utilized the delayed coincidence method and a timing spectrometer system of fast plastic scintillators. No attempts were made in that investigation to correct the experimental results for gamma-ray misidentification as the corrections were assumed to be small. Therefore, the current investigation was undertaken to test the validity of that assumption. In this study a high resolution Ge (Li) detector was used with the Collins system to determine the percentages of misidentifications; corrections were then obtained for the previously determined experimental lifetime values.Collins obtained half-lifetimes of 1.5 ± 1.0 psec and 5.1 ± 0.5 psec for the first and second excited states, respectively, of 144Nd. After corrections were applied to these results, the half-lifetimes of the first and second excited states were corrected to 2.8 ± 1.0 psec and 7.4 ± 0.9 psec, respectively. The half-lifetime value of the second excited state, 7.4 ± 0.9 psec, is in disagreement with previous reported values of 21 ± 2 psec and 100 ± 30 psec, all of which were calculated by delayed-coincidence method. The first excited state of 144Nd has a measured lifetime of 3.4 ± 0.1 psec obtained from Coulomb excitation studies. The corrected value of 2.8 { 1.0 psec obtained in this study, therefore, lies within the accepted region for this same level. Since the latter value appears to be in agreement with accepted values, then the value for the calculated half-lifetime of 7.4 ± 0.9 psec for the 1314-keV level can be accepted with greater confidence.