Nature of the first excited state of $^{4}$ He

We study the first excited state of

^{4}

He in a microscopic

{^{3} H {+ p,}^{3} He + n}

cluster model, including

^{3}

H and

^{3}

He distortions. The phenomenological

^{1} S_{0}

^{3} H + p

scattering phase shift is reasonably well reproduced. We localize a complex pole of the

S

matrix between the

^{3} H + p

and

^{3} He + n

thresholds. The corresponding resonance parameters are

E_{r} = 93

keV position relative to

^{3} H + p

, and

Γ = 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

Γ = 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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Nature of the first excited state of4He