We report an observation of long-lived spin-singlet states in a 13C-1H spin pair in a zero magnetic field. In 13C-labeled formic acid, we observe spin-singlet lifetimes as long as 37 s, about a factor of 3 longer than the T1 lifetime of dipole polarization in the triplet state. In contrast to common high-field experiments, the observed coherence is a singlet-triplet coherence with a lifetime T2...

We review the Bethe-Salpeter equation (BSE) approach to the calculation of electronic excitation energies of molecular systems. We recall the general Green’s function many-theory formalism and give the working equations of the BSE approach within the static GW approximation with and without spin adaptation in an orbital basis. We apply the method to the pedagogical example of the H2 molecule in...

Abstract. In present work the effective singlet-triplet model for CuO2-layer in the framework of multiband p-d model of strongly correlated electrons is obtained. The resulting Hamiltonian has a form of generalized singlet-triplet t-t’-J model for p-type superconductors and form of usual t-t’-J model for n-type superconductors. In the mean field approximation in X-operator representation we der...

2014 Radiative lifetime for 17 vibrational levels corresponding to 7 singlet and 3 triplet electronic states have been measured by using a delayed-coincidence method. We report first measurements of four H2 levels of which lifetimes range from 34 to 110 ns. J. Phys. France 49 (1988) 445-449 MARS 1988, Classification Physics Abstracts 34.80G

We synthesized a series of purely organic phosphors, bromobenzaldehyde derivatives, with varying conjugation length to investigate the effects of conjugation length on their phosphorescence emission properties. As the conjugation length increases phosphorescence efficiency decreases with a redshift in the emission color at 77 K. Our computational results imply that this correlation is related t...

Three kinds of magnetic resonance signals were detected in crystals of the spin-gap magnet TlCuCl3. First, we have observed the microwave absorption due to the excitation of the transitions between the singlet ground state and the excited triplet states. This mode has the linear frequency-field dependence corresponding to the previously known value of the zero-field spin-gap of 156 GHz and to t...

We have studied the evolution of the T1 triplet excited state in an extensive series of phenylene ethynylene polymers and monomers with platinum atoms in the polymer backbone and in an analogous series of all-organic polymers with the platinum~II! tributylphosphonium complex replaced by phenylene. The inclusion of platinum increases spin–orbit coupling so T1 state emission ~phosphorescence! is ...

Density functional theory (B3LYP/6-31G(d,p)) was used to predict the effect of meta substitution on aryl cationic (Ar-X+) species, including aryloxenium ions, arylsilylenium ions, arylnitrenium ions, and arylcarbenium ions. Multireference second-order perturbation theory (CASPT2) calculations were used to benchmark the quantitative accuracy of the DFT calculations for representative systems. Su...

We report magnetic susceptibility, specific heat, and neutron scattering measurements as a function of applied magnetic field and temperature to characterize the S = 1/2 quasi-two-dimensional frustrated magnet piperazinium hexachlorodicuprate (PHCC). The experiments reveal four distinct phases. At low temperatures and fields the material forms a quantum paramagnet with a 1 meV singlet triplet g...