The 77 K emission spectral maxima of bis(bipyridine)ruthenium(II) complexes are found to approach a limit at energies below about 14,000 cm(-1). There is also evidence for related low-energy excited-state limits in some other classes of ruthenium polypyridyl complexes. The shapes of the vibronic sidebands found in these limits differ from those of complexes that emit at higher energies. These l...

Context. Absorption of ultraviolet radiation by water ice coating interstellar grains can lead to dissociation and desorption of the ice molecules. These processes are thought to be important in the gas-grain chemistry in molecular clouds and protoplanetary disks, but very few quantitative studies exist. Aims. We compute the photodesorption efficiencies of amorphous water ice and elucidate the ...

Photophysical and photochemical dynamics of ground state and excited state proton transfer reaction is reported for Pyrrole 2-Caboxyldehyde (PCL). Steady state absorption and emission measurements are conducted in this five member heterocyclic system (PCL). The theoretical investigation is done by using different quantum mechanical methods (e.g. Hartree Fock, DFT, MP2, CCSD etc.). The reaction ...

The excited-state intramolecular H-atom transfer reactions of hypocrellins B and A are compared with those of calphostin C. On the basis of the results of transient absorption measurements and ab initio quantum mechanical calculations, it is concluded that large-amplitude conformational changes are coupled to the Hatom transfer in calphostin C, just as they are in hypocrellins A and B. The calc...

An ab initio excited state potential energy surface is constructed for describing excited state double proton transfer in the tautomerization reaction of photo-excited 7-azaindole dimers, and the ultrafast dynamics is simulated using the semiclassical ~SC! initial value representation ~IVR!. The potential energy surface, determined in a reduced dimensionality, is obtained at the CIS level of qu...

The U(5) − O(6) transitional behavior of the Interacting Boson Model in the large N limit is revisited. Some low-lying energy levels, overlaps of the ground state wavefunctions, B(E2) transition rate for the decay of the first excited energy level to the ground state, and the order parameters are calculated for different total numbers of bosons. The results show that critical behaviors of these...

The modification of reaction centers from Rhodobacter sphaeroides by the introduction of pheophytins instead of bacteriopheophytins leads to interesting changes in the primary photosynthetic reaction: long-living populations of the excited electronic state of the special pair P* and the bacteriochlorophyll anion Bi show up. The data allow the determination of the energetics in the reaction cent...

The excited state lifetimes of DNA bases are often very short due to very efficient non-radiative processes assigned to the ππ*-nπ* coupling. A set of protonated aromatic diazine molecules (pyridazine, pyrimidine and pyrazine C4H5N2(+)) and protonated pyrimidine DNA bases (cytosine, uracil and thymine), as well as the protonated pyridine (C5H6N(+)), have been investigated. For all these molecul...

The dynamics of Cl~P! atoms in a solid Ar matrix is studied, with emphasis on electronic energy relaxation of excited states, and on p-orbital reorientation effects. The method used follows Tully’s approach for nonadiabatic molecular dynamics simulations, which treats the electronic degrees of freedom quantum-mechanically, and the atomic motions classically, allowing for ‘‘hopping’’ of the atom...