We have extended our past measurements of the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(t,α)n reaction near the low-energy ${\mathrm{}(3/2)\mathrm{}}^{+}$ resonance by measuring eight more data points over the lab deuteron energy range 80–116 keV. This was accomplished by bombarding a tritium gas target with deuterons, in contrast to the previous measurements in which a deuterium gas target was bombarded with tritons. The present data are accurate to 1.6%. The results of including the present data in a simple two-channel, two-level, R-matrix analysis and also in a large three-channel, multilevel, R-matrix analysis are presented. The resonance is characterized by giving the S-matrix poles from the R-matrix analyses. Of interest is the discovery that both analyses give two resonance poles on different (unphysical) Riemann sheets, one of them being a so-called ‘‘shadow pole.’’ This is the first experimental observation of a shadow pole in nuclear and particle physics. Maxwellian reactivities up to a plasma temperature of 20 keV are presented.

• Received 9 March 1987

DOI:https://doi.org/10.1103/PhysRevC.35.1999