Computation of the complex energy shift of decaying states in intense laser fields.

We present a specific calculation concerning laser-assisted decaying systems with non-Hermitian spectral calculations merged with the (t,t')-formalism to estimate the possible intense laser-field-induced corrections to the lifetime of quasi-stationary states. The perturbed complex energy shift caused by the external vector potential which represents the linearly and circularly polarized laser field is calculated in details. This wavefunction-centered method implies the unsuitability of the radiation gauge and length gauge when quasi-stationary states are considered and described within the framework of non-hermitian quantum mechanics since in this case the A 2 term cannot be transformed out. • Perturbative description of quasi-stationary states in intense laser-fields. • Time-dependent perturbation in the framework of the (tt') formalism. • Resonant states in laser-pulses. [ABSTRACT FROM AUTHOR]