NATURE OF THE FIRST EXCITED-STATE OF HE-4

We study the first excited state of He-4 in a microscopic {H-3+p,He-3n} cluster model, including H-3 and He-3 distortions. The phenomenolog ical S-1(0) H-3+p scattering phase shift is reasonably well reproduced . We localize a complex pole of the S matrix between the H-3+p and He- 3+n thresholds. The corresponding resonance parameters are E-r = 93 ke V position relative to H-3+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 E-r = 114 keV and Gamma = 392 keV. The R-matrix approach gives several additional poles, some of which may be connecte d with an enhanced threshold effect.