  We present a non-Hermitian theory of atomic and molecular absorption, which
enables computing the absorption spectrum of multi-electron atoms and molecules
without using any fitting parameters. We propose a method for optically
inducing exceptional points in atomic systems, and show that slight changes in
the laser parameters may lead to dramatic changes in the absorption lineshape.
We demonstrate these predictions for helium using exact ab-initio
electronic-structure data. Finally, we derive a simple formula for the Fano
asymmetry factor and evaluate it for a model xenon atom.
