Elastic $p$-${\mathrm{He}}^3$ scattering was measured in an attempt to obtain further information regarding the possible existence of a state in ${\mathrm{Li}}^4$ near 10.6 MeV of width ≤400 keV, which has been inferred from observations of ${}_{\Lambda }{}^{}{}_{}{}^{}\mathrm{He}_{}^4{}_{}{}^{}$ decay. In view of the possibly very small width of the state, experimental details were arranged to permit observation associated with widths as small as 25 keV. Differential elastic-scattering cross sections were measured at center-of-mass angles of 70.9°, 91.1°, 104.4°, and 112.0° and over a laboratory energy range of 11.6 to 16.4 MeV in 25-keV steps. The measured cross sections decreased slowly with increasing energy, and no evidence of a resonance was observed. Therefore, we conclude that if a $1^{-}$ state in ${\mathrm{Li}}^4$ near 10.6 MeV decays predominantly in the $p$-${\mathrm{He}}^3$ channel, the width of the state must be less than 25 keV.

• Received 3 October 1966

DOI:https://doi.org/10.1103/PhysRev.154.950