Nature of the first excited state of He-4
Abstract
We study the first excited state of He4 in a microscopic H3+p,He3+n cluster model, including H3 and He3 distortions. The phenomenological 1S0 H3+p scattering phase shift is well reproduced. We localize a complex pole of the S-matrix between the H3+p and He3+n thresholds. The corresponding resonance parameters are Er=93 keV position relative to H3+p, and Gamma=390 keV width. A pole search is also performed in an extended R-matrix method, and a resonance is found with parameters Er=114 keV and Gamma=392 keV. The R-matrix approach gives several additional poles, some of which may be connected with an enhanced threshold effect.
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