We present a detailed numerical analysis of the low-energy excitation spectrum of a frustrated and dimerized spin S51/2 Heisenberg chain. In particular, we show that in the commensurate spin-Peierls phase the ratio of the singlet and triplet excitation gap is a universal function which depends on the frustration parameter only. We identify the conditions for which a second elementary triplet br...

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than ...

The reaction dynamics of the dicarbon molecule with D3-methylacetylene, CD3CCH(X A1), were investigated utilizing the crossed molecular beams approach. By combining the experimental results on the atomic hydrogen versus deuterium loss channels with electronic structure calculations, we could substantiate that the D3CCCCC(X A) radical is neither formed on the singlet nor on the triplet surface. ...

We introduce a broadly applicable technique to create nuclear spin singlet states in organic molecules and other many-atom systems. We employ a novel pulse sequence to produce a spin-lock induced crossing (SLIC) of the spin singlet and triplet energy levels, which enables triplet-singlet polarization transfer and singlet-state preparation. We demonstrate the utility of the SLIC method by produc...

the combined effect of hydrostatic pressure and temperature on correlation energy in a triplet state of two electron spherical quantum dot with square well potential is computed. the result is presented taking gaas dot as an example. our result shows the correlation energies are i)negative in the triplet state contrast to the singlet state ii) it increases with increase in pressure  iii)further...

Singlet fission, the conversion of a singlet excitation into two triplet excitations, is a viable route to improved solar-cell efficiency. Despite active efforts to understand the singlet fission mechanism, which would aid in the rational design of new materials, a comprehensive understanding of mechanistic principles is still lacking. Here, we present the first study of singlet fission in crys...

Saturation of complex molecules affects the nonlinear processes occurring in medium. The medium can be described by two-, three-, and four-level configurations. principal singlet-singlet excited triplet-triplet channels a four-level, N-type, configuration were used to study medium, which was radiation with two frequencies. Under weak population energy levels channel (a small ratio total probabi...

The reaction pathways for the photochemical formation of cyclobutane thymine dimers in DNA are explored using hybrid density functional theory techniques. It is concluded that the thymine-thymine [2 + 2] cycloaddition displays favorable energy barriers and reaction energies in both the triplet and the singlet excited states. The stepwise cycloaddition in the triplet excited state involves the i...

Fullerene C60 derivatives covalently linked to a nitroxide radical are studied by Time Resolved EPR. The interaction between radical and triplet or singlet excitation, localized on the fullerene moiety, gives rise to spin polarization of the radical EPR signal. The quartet state of the Radical Triplet Pair (RTP) is also observed by EPR. Electron transfer involving the excited fullerene triplet ...