ITAMP Topical Lunch Discussion Date: FRIDAY, April 11 Time: 12:00-1:30 pm Pizza will be served. Location: B-106 @ Center for Astrophysics (60 Garden Street) Directions: after entering the lobby of the CfA, turn right to enter the hallway of the B building. In the hallway, turn right again, and B-106 is there. *Speaker*: Prof. Ksenia Bravaya (Boston University) *Title:* Electronic structure theory for autoionizing electronic states: challenges and prerequisites. *Abstract:* Autoionizing electronic states are ubiquitous in highly energetic environment; they also play an important role in the photophysics of anions (including biochromophores) and in the condensed phase processes, e.g. DNA damage by secondary electrons. Accurate prediction of the lifetimes of autoionizing states is crucial for understanding the dynamics and chemical properties of these systems. I will discuss a new set of methods we developed to extend the capabilities of conventional high-level electronic structure methods to the description of resonance energies and life-times. The methods are based on combining accurate equation-of-motion coupled-cluster (EOM-CC) approaches with complex-scaling and complex-absorbing potential techniques. The latter two approaches allow one to isolate a resonance as a single L^2-inetegrable eigenstate of the modified non-Hermitian Hamiltonian. Real and imaginary parts of the corresponding complex eigenvalue give resonance position and width, respectively. I will show results of some benchmark calculations, including atoms and small molecules, discuss the importance of the electron correlation in description of Feshbach and shape resonances, and formulate current challenges for the theory and potential solutions.