Recent results of laser spectroscopy experiments of pionic helium atoms at PSI

Abstract

A review of a recent experiment carried out at PSI involving laser spectroscopy of metastable pionic helium (\pi{^4He}^+\equiv\pi^{-}+{^4He}^{2+}+e^-π4He+≡π−+4He2++e−) atoms is presented. An infrared transition (n,\ell)=(17,16)(n,ℓ)=(17,16)\rightarrow→(17,15)(17,15) at a resonance frequency of \nu\approx 183760ν≈183760 GHz was detected.