Effective Fragment Potentials for Microsolvated Excited and Anionic States.

The effective fragment potential (EFP) approach is a sophisticated hybrid approach that allows the inclusion of solvation effects when describing properties and reactivity in the condensed phase, without using empirical parameters. This work examines the performance of the EFP method when describing microsolvation in electronically excited states of neutrals and anions. The examples selected include both localized valence states, as well as diffuse nonvalence states, which represent greater challenges to conventional electronic structure methods.

Spectroscopy and Theoretical Modeling of Tetracene Anion Resonances.

The positions and widths of the optically allowed electronic states of the tetracene radical anion located above the detachment threshold energy (i.e anion resonances) are mapped out using total photodetachment yield spectroscopy of cryogenically cooled ions. The presence of these states is detected via the sharp increase in the photodetachment yield compared to that of the monotonic nonresonant direct photodetachment background.

Projected Complex Absorbing Potential Multireference Configuration Interaction Approach for Shape and Feshbach Resonances.

Anion resonances are formed as metastable intermediates in low-energy electron-induced reactions. Due to the finite lifetimes of resonances, applying standard Hermitian formalism for their characterization presents a vexing problem for computational chemists. Numerous modifications to conventional quantum chemical methods have enabled satisfactory characterization of resonances, but specific issues remain, especially in describing two-particle one-hole (2p-1h) resonances.

A Unique QP Partitioning and Siegert Width Using Real-Valued Continuum-Remover Potential.

A simple, practical quantum chemical procedure is presented for computing the energy position and the decay width of autoionization resonances. It combines the -stabilized resonance wave function obtained using the real-valued continuum-remover (CR) potential [Y. Sajeev , , 105-112] and the Feshbach projection operator (FPO) partitioning technique.

A Simple and Efficient Method for Simulating the Electronic Absorption Spectra of Criegee Intermediates: Benchmarking on CHOO and CHCHOO.

Criegee intermediates (CIs) play a vital role in the atmosphere-known most prominently for enhancing the oxidizing capacity of the troposphere. Knowledge of their electronic absorption spectra is of vital importance for two reasons: (1) to aid experimentalists in detecting CIs and (2) in deciding if their removal is affected by solar photolysis. In this article we report a simple and efficient method based on the nuclear ensemble method that may be effectively used to compute the electronic absorption spectra of Criegee intermediates without the need for extensive computation of preparing the initial configurations of the starting geometry.

Description of Two-Particle One-Hole Electronic Resonances Using Orbital Stabilization Methods.

Two-particle one-hole (2p-1h) resonances are elusive to accurate characterization, their decay to the neutral state being a two-electron process. Although in limited cases, single reference methods can be used, a proper description of a 2p-1h resonant state entails a multiconfigurational treatment of the reference wavefunction. In this work, we test the performance of the orbital stabilization method to characterize the 2p-1h resonances found in water and benzene.

Comparative study of methodologies for calculating metastable states of small to medium-sized molecules.

We present a benchmarking study on the performance of two methods at the forefront of studying electronic metastable states of molecules: the orbital stabilization method and the method of complex absorbing potential augmented Hamiltonians. The performance of the two methods is compared for the calculation of shape resonances in small to medium-sized molecules (up to 15 atoms) at the equation of motion coupled cluster with singles and doubles for the electron attachment level of methodology using even-tempered Gaussian basis sets. The theoretical positions and widths of shape resonances obtained from both methods are compared to the experimentally determined electron affinities and lifetimes.