dc Stark effect for doubly excited Feshbach resonance states of the positronium negative ion below the N=2 threshold of a positronium atom

We present a study of the influence of a constant uniform electric field on the doubly excited resonances of the negative positronium ion associated with the N=2 positronium threshold. The calculation is performed in the framework of the complex coordinate rotation method, allowing us to obtain positions and widths of the resonance states. Results are given for the M=0 Stark components of the following Feshbach resonances associated with the N=2 positronium threshold: ¹S^e(1), ¹S^e(2), ¹S^e(3), ¹P^o(1), ¹P^o(2), ¹D^e(1), and ¹D^e(2).