States in ⁹⁶Tc populated in the (α,n) reaction

Abstract

<p>The levels of odd-odd ⁹⁶Tc were investigated using the ⁹³Nb(α,n)⁹⁶Tc reaction at alpha beam energies of 14 and 18 MeV. The experiments involved singles, gamma-gamma coincidences, neutron-gamma coincidences, excitation functions, gamma-ray angular distributions, measurements of the gamma-ray linear polarization coefficients and electron internal conversion coefficients. At 14 MeV a rich level structure was established involving low-lying states of low and medium spins and both parities. The position of the positive parity sextet of levels resulting from the coupling of an odd g₉/₂ proton to an odd d₅⁄₂ neutron was clarified to be: 7⁺ ground state, 34.4 keV (4⁺), 35.6 keV ((2)⁺), 36.4 keV (3⁺), 45.3 keV (5⁺) and 49.3 keV (6⁺). The measurements performed with 18 MeV beam revealed an extensive high-spin positive parity level structure extending in excitation energy up to ~ 3 MeV and populating levels of spin up to 13. Spin and parity assignments are given with a high degree of confidence to most of the 105 energy levels. These states are connected by 251 gamma-ray transitions. Attempts have been made to relate this level structure to those of other nuclei in the nass 100 region.</p> <p>A new method of spin assignment using the maxima of the excitation functions following the (α,n) reaction has been proposed. A theoretical justification for this apparently empirical method is developed using the Hauser-Feshbach formalism. This theory also gives a strong theoretical basis for a method of spin assignment based on the ratio of gamma-ray intensities obtained at two beam energies.</p> <p>Theoretical estimates of attenuation coefficients for angular distributions following (Heavy Ion, xn) reaction are provided. These involved modifying existing methods to make them applicable to nuclei with high spin ground states.</p>