Vertical and adiabatic excitation energies of the lowest (2)A(') excited state in the water-hydroxyl complex have been determined using coupled cluster, multireference configuration interaction, multireference perturbation theory, and density-functional methods. A significant redshift of about 0.4 eV in the vertical excitation energy of the complex compared to that of the hydroxyl radical monom...

We present a method for obtaining outer-valence quasiparticle excitation energies from a density-functional-theory-based calculation, with an accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with an asymptotically exact and short-range fractional Fock exchange. The functional contains...

The first vacuum-ultraviolet absorption spectrum of pyridine-N-oxide has been obtained, and has led to the identification of nearly 30 Rydberg states. These states were identified by use of the vibrational envelope ("footprint") of the UV-photoelectron spectrum, and are based on the first to the third ionization energies (IE). The adiabatic IE order, central to the Rydberg state symmetry identi...

Raman scattering experiments on stoichiometric, Mott-insulating LaTiO_{3} over a wide range of excitation energies reveal a broad electronic continuum which is featureless in the paramagnetic state, but develops a gap of ~800 cm^{-1} upon cooling below the Néel temperature T_{N}=146 K. In the antiferromagnetic state, the spectral weight below the gap is transferred to well-defined spectral feat...

The photophysics of indigo as well as of bispyrroleindigo, the basic chromophore of indigo, has been investigated with ab initio electronic-structure calculations. Vertical electronic excitation energies and excited-state potential-energy profiles have been calculated with the CASSCF, CASPT2 and CC2 methods. The calculations reveal that indigo and bispyrroleindigo undergo intramolecular single-...

We examine the transfer of electronic excitation (an exciton) along a chain of electronically coupled monomers possessing internal vibronic structure and which also interact with degrees of freedom of the surrounding environment. Using a combination of analytical and numerical methods, we calculate the time evolution operator or time-dependent Green's function of the system and thereby isolate ...

We investigate the influence of low-energy recoils with respect to the electronic excitation of solids generated in atomic collision cascades. It is found that the electronic friction experienced by recoil atoms moving with kinetic energies below 10 eV contributes substantially to the total excitation energy dissipated into electronic degrees of freedom. The collision dynamics, on the other han...

The generator-coordinate method is a flexible and powerful reformulation of the variational principle. Here we show that by introducing a generator coordinate in the Kohn-Sham equation of density-functional theory, excitation energies can be obtained from ground-state density functionals. As a viability test, the method is applied to ground-state energies and various types of excited-state ener...

We investigate the time-dependent evolution of a nonstationary three-body Coulomb system at energies just below the threshold for three-body breakup. Experimentally, short-pulse lasers excite two electrons in Ba to radially localized Rydberg wave packets with well-defined energy and angular momentum. Time-dependent interactions between the two electrons are probed using half-cycle electric fiel...

Positron annihilation on many molecules occurs via positron capture into vibrational Feshbach resonances, with annihilation rates often further enhanced by energy transfer to vibrational excitations weakly coupled to the positron continuum. Data presented here uncover another scenario in which the positron couples directly to a quasicontinuum of multimode vibrational states. A model that assume...