Pb208(d, α)Tl206Reaction and theπ−1ν−1Structure ofTl206

Abstract

The proton-neutron hole states of ${\mathrm{Tl}}^{206}$ have been studied by the direct ${\mathrm{Pb}}^{208}(d, \ensuremath{\alpha}){\mathrm{Tl}}^{206}$ reaction with 17-MeV deuterons. Experimental resolutions of 12-15 keV for about 28-MeV $\ensuremath{\alpha}$ particles permitted the investigation of many two-hole states previously unknown. For most levels, $L$ values could be extracted from the comparison of microscopic two-nucleon transfer distorted-wave Born-approximation (DWBA) calculations with experimental angular distributions. The experimental level energies and ${J}^{\ensuremath{\pi}}$ assignments (or limits) were compared where possible to recent ($n, \ensuremath{\gamma}$) and ($t, \ensuremath{\alpha}$) data for ${\mathrm{Tl}}^{206}$ and to structure calculations by Kuo. It was possible to correlate about 20 low-lying levels (${E}_{x}\ensuremath{\lesssim}2.2$ MeV) with calculated shell-model states. In addition, Kuo's wave functions were used to derive detailed ($d, \ensuremath{\alpha}$) cross-section intensity distributions, and to check the dependence of the absolute normalization constant $N(d, \ensuremath{\alpha})$ on various DWBA parameters. Constructive coherence in the transition amplitudes predicted by the wave functions for the lowest states of a given ${J}^{\ensuremath{\pi}}$ was varified experimentally. Ten enhanced ($d, \ensuremath{\alpha}$) cross sections are observed, in good qualitative agreement with theoretical predictions. The predicted enhancement for the population of some of these states was occasionally in excess of the observed enhancement.