  We present an efficient implementation of the second- and third-order
single-reference algebraic diagrammatic construction theory for electron
attachment (EA) and ionization (IP) energies and spectra (EA/IP-ADC(n), n = 2,
3). Our new EA/IP-ADC program features spin adaptation for closed-shell
systems, density fitting for efficient handling of the two-electron integral
tensors, as well as vectorized and parallel implementation of tensor
contractions. We demonstrate capabilities of our efficient implementation by
applying the EA/IP-ADC(n) (n = 2, 3) methods to compute the photoelectron
spectrum of the TEMPO radical, as well as the vertical and adiabatic electron
affinities of TEMPO and two DNA base pairs (guanine-cytosine and
adenine-thymine). The spectra and electron affinities computed using large
diffuse basis sets with up to 1028 molecular orbitals are found to be in a good
agreement with the best available results from the experiment and theoretical
simulations.
