Nuclear Levels inPr142

Abstract

A combination of ($d,p$)-reaction spectroscopy and high- and low-energy $\ensuremath{\gamma}$ rays following thermal-neutron capture in $^{141}\mathrm{Pr}$ has been used to study the levels in $^{142}\mathrm{Pr}$. The ($d,p$) reaction populates 65 states below 2 MeV, whereas 37 states below 2 MeV are populated by high-energy $\ensuremath{\gamma}$ transitions from thermal-neutron capture. The ground-state $Q$ value determined in the ($d,p$) reaction is 3622\ifmmode\pm\else\textpm\fi{}3 keV, in agreement with the neutron binding energy of 5843.4\ifmmode\pm\else\textpm\fi{}1.5 keV. Differential cross sections were measured at nine angles for the ($d,p$) reaction and interpreted in terms of the distorted-wave Born-approximation reaction theory. Utilizing, in addition, some of the low-energy $\ensuremath{\gamma}$ rays observed with a bent-crystal spectrograph and with a Ge(Li) spectrometer, it has been possible to make the following assignments (energy in keV, spin and parity in parentheses): ground state, (2---); 3.683, (5---); 17.740, (3---); 63.746, (6---); 72.294, (4---); 84.998, (1---); 128.251, (5---); 144.587, (4---); 176.863, (3---); and 200.525, (2---). These states are interpreted in terms of configuration mixing between the two configurations $\ensuremath{\pi}{{d}_{\frac{5}{2}}}^{1}\ensuremath{\nu}{{f}_{\frac{7}{2}}}^{1}$ and $\ensuremath{\pi}{{g}_{\frac{7}{2}}}^{\ensuremath{-}1}\ensuremath{\nu}{{f}_{\frac{7}{2}}}^{1}$. Not only the energies of the levels but also the transition probability ratios are consistent with this interpretation. The calculated half-life of the 3.683 keV, 5--- isomeric state is in reasonable agreement with the experimental value. Tentative spin and parity assignments have been made to levels above 250 keV.