Resonance phenomena play an important role in diverse areas of science from photoelectron spectroscopy to molecular electronics and strong-field physics. Their efficient and reliable theoretical description has proven to be difficult in Hermitian quantum mechanics as they cannot be associated with a single discrete eigenstate of the Hamiltonian and belong to the continuum part of the spectrum. Hence, they are beyond the reach of standard quantum-chemical methods. A viable and elegant treatment of resonances is, however, possible when they are described as metastable electronic states separated from the continuum. This can be achieved with techniques developed in non-Hermitian quantum mechanics such as complex-absorbing potentials (CAPs). In this talk, an implementation of CAPs for use with equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) –a method known for its reliability in electronic-structure calculations– into the Q-Chem package is presented together with a protocol to treat metastable states in an accurate manner. The advantages of EOM-CC theory over using state-specific approaches such as Hartree-Fock or CC theory are illustrated. Applications to autodetachment processes demonstrate that CAP-EOM-CCSD agrees quantitatively with experimental results from photodetachment spectroscopy. Also, it is shown how metastable states can be characterized using quantities such as Dyson orbitals and transition dipole moments. [1] T.-C. Jagau, D. Zuev, K. B. Bravaya, E. Epifanovsky, and A. I. Krylov, J. Phys. Chem. Lett. 5, 310 (2014). [2] D. Zuev, T.-C. Jagau, K. B. Bravaya, E. Epifanovsky, Y. Shao, E. Sundstrom, M. Head-Gordon, and A. I. Krylov, J. Chem. Phys. 141, 024102 (2014). [3] T.-C. Jagau and A. I. Krylov, J. Phys. Chem. Lett. 5, 3078 (2014). [4] T.-C. Jagau, D. B. Dao, N. S. Holtgrewe, A. I. Krylov and R. Mabbs, J. Phys. Chem. Lett. 6, 2786 (2015). [5] Y. Shao et al., Mol. Phys. 113, 184 (2015).

Complex-absorbing potentials in equation-of-motion coupled-cluster theory

251st National Meeting (2016)

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