Polarizability of the pionic helium atom

The static dipole polarizability of metastable states in pionic helium atoms is studied. We use the complex coordinate rotation method to properly take account of the resonant nature of the states. Our calculation shows that the (17, 14) states both in ³He and ⁴He are not stable due to strong collisional quenching. This explains the absence of signal in the PiHe experiment at the Paul Scherer Institute, Switzerland while studying the (16, 15) $\to$ (17, 14) transition. (paper)