Linear and non-linear optical properties of indeno[2,1-b]fluorene (1) and its structural isomers with 20 π-electrons have been studied using many body methods. As compared to other π electron systems of similar conjugation length, the experimentally measured optical gap (vertical excitation energy) and the singlet-triplet gap of 1 are quite small. The diradical character calculated using the ab...

Polarization-dependent resonant inelastic x-ray scattering (RIXS) is shown to be a new probe of molecular-field effects on the electronic structure of isolated molecules. A combined experimental and theoretical analysis explains the linear dichroism observed in Cl 2p RIXS following Cl 1s excitation in HCl and CF3Cl as due to molecular-field effects, including singlet-triplet exchange, indicatin...

They are important chemical intermediates whose spin state dependent chemistry is implicated in a large number of organic reactions [l-4]. An important feature relevant to an understanding of many of their physical and chemical properties is the small energy gap separating the lowest singlet and triplet states. In fact for a number of carbenes these two states are in equilibrium at room tempera...

Using parameter values relevant to polyacetylene and its finite polyene analogs, we determine, via exact finite size diagonalization of a 1D Peierls-Hubbard model, the relaxed geometry and optical absorption spectra of several states of interest in optical experiments (the singlet (1Ag) and triplet (1Bu) ground states, the singlet one (n Bu) and two (2 Ag) photon gaps, and the triplet one (n Ag...

We have performed time-of-flight neutron scattering measurements on powder samples of the unconventional spin-Peierls compound TiOBr using the fine-resolution Fermi chopper spectrometer (SEQUOIA) at the Spallation Neutron Source at Oak Ridge National Laboratory. These measurements reveal two branches of magnetic excitations within the commensurate and incommensurate spin-Peierls phases, which w...

The primary step currently assumed in bacterial photosynthesis involves fast electron transfer between the electronically excited bacteriochlorophyll ‘special pair’ [l], ’ (BChl):, and a bacteriopheophytin, BPh, with a rate kR > (10 ps)-’ [2-41. In blocked reaction centers, the radical ions thus formed live for G 10 ns at 300 K [5] and decay by the back transfer of the electron. If this occurs ...

The molecular mechanism of the thermal rearrangement of singlet 1H-bicyclo[3.1.0]hexa-3,5-dien-2-one to give triplet 4-oxocyclohexa-2,5-dienylidene has been investigated using density functional theory (B3LYP and M05-2X functionals) as well as ab initio CASSCF and CASPT2 multiconfigurational methods. The reactant has a singlet ground state while the product can be found in three low lying elect...

The influence of heavy atom substituents (Br, I) in the electron donor aniline on the electron transfer reaction with thiopyronine triplet is investigated by flash spectroscopy in solvents of different viscosity and polarity. Triplet quenching constants and radical yields are determined. The results are analysed in terms of decay constants of an intermediate triplet exciplex where the heavy ato...

The intersystem crossing rate for the transition between the lowest excited singlet and triplet electronic states of uracil was studied by means of ab initio methods. The rate was evaluated using the time-dependent approach based on the correlation function and its two approximations: the second-order cumulant expansion and the short-time approximation. The normal modes of the singlet and tripl...

We derive gap equations for superconductivity in coexistence with ferromagnetism. We treat singlet states and triplet states with either equal spin pairing (ESP) or opposite spin pairing (OSP) states, and study the behaviour of these states as a function of exchange splitting. For the s-wave singlet state we find that our gap equations correctly reproduce the Clogston–Chandrasekhar limiting beh...