The rate constants k b - a and k a - X of the b1Σg + → a1Δg and a1Δg → X3Σg - emissions of O2 have been determined in liquid CCl4, C2Cl4, and C4Cl6. The ratios k a - X/k b - a range from 4.4 × 10-4 (CCl4) to 8 × 10-4 (C4Cl6). In addition, rate constants k a - X have been determined in several solvents and in the binary solvent mixtures H2O/acetone, acetone/C6H6, and CH3OH/CHCl3. k a - X depends for H2O/acetone and CH3OH/CHCl3 in a strongly anomalous way on the bulk polarizability P of the solvent, demonstrating that no general smooth correlation of k a - X with P exists. Our results confirm the perturbation model developed by Minaev. According to this model, the collision-enhanced b → a radiative transition lends intensity to the transition a → X. Both radiative transitions are bimolecular processes. For the pure solvents, the second-order rate constants correlate roughly with the square of the molar refraction R of the solvent. If the effects of the solvent refractive index, of the collision frequency, and of the dependence of the probability P a - X of the collision-induced radiative transition per collision on the size of the collider, are removed, a direct and linear proportionality of the transition moment of the collision-induced emission with the collider's molecular polarizability is discovered. For mixtures, k a - X is additively composed of the contributions of the individual components. These results explain for the first time consistently and quantitatively the solvent effects on k a - X.

Large sets of literature data on the enhancement of the O2 emissions a1Δg → X3Σg - in solution and b1Σg + → alΔg in the gas phase have been analyzed. Second-order rate constants have been interpreted with respect to molecular parameters such as collision frequency, molecular size, and molecular polarizability of the collider. It is shown that the transition moments of both collision-induced radiative transitions are directly proportional to the molecular polarizability of the collider, if the effects of collider size and collision frequency are removed. A transient shift of electron density from the collider MOs into the πg, x and πg, y molecular orbitals of O2 occurs, which induces electric dipole character into the b → a transition. Because of the strong spin-orbit coupling of O2, the a → X transition profits proportionally from the enhancement of the b → a transition by intensity borrowing.

Rate constants kq of the quenching of singlet oxygen in its a1Δg‐state by five amines (piperazine (P), N,N′‐dimethylpiperazine (DMP), N‐methylpiperidine (MPP), quinuclidine (Q), N,N,N′,N′‐tetramethylphenylene‐1,4‐diamine (TMPD)) have been determined in solvents with different polarity in dependence on pressure up to 1200 or 1600 bar using time‐resolved phosphorescence techniques. In the case of the efficient O2(a1Δg) quencher TMPD in o‐dichlorobenzene and in benzonitrile at about 700 bar the transition is observed from the reaction‐controlled rate to the diffusion‐controlled rate limit. For all amines the highest negative value of the experimental activation volume was found in n‐hexane (−33.0 ≥ ΔV ±exp ≥ −42.0 cm3 · mol−1) and the lowest negative value in benzonitrile (−9.0 ≥ ΔV ±exp ≥ −19.0 cm3 mol−1). These results are consistent with the assumption that quenching of O2(a1Δg) by amines occurs via polar exciplexes with singlet and triplet multiplicity, respectively. The data were analysed taking into account contact complex formation. The reaction volume ΔVc of the formation of the contact complex was evaluated using the statistical model developed by Yoshimura and Nakahara. On the basis of Kirkwoods electrostriction model the dipole moments of the singlet exciplexes were calculated in the range between 5.7 (P) and 11.5 Debye (TMPD), indicating that only a partial charge transfer takes place in the quenching process.

The dynamic response of ultracold Bose gases in one-dimensional optical lattices and superlattices is investigated based on exact numerical time evolutions in the framework of the Bose-Hubbard model. The system is excited by a temporal amplitude modulation of the lattice potential, as it was done in recent experiments. For regular lattice potentials, the dynamic signatures of the superfluid to Mott-insulator transition are studied and the position and the fine-structure of the resonances is explained by a linear response analysis. Using direct simulations and the perturbative analysis it is shown that in the presence of a two-colour superlattice the excitation spectrum changes significantly when going from the homogeneous Mott-insulator the quasi Bose-glass phase. A characteristic and experimentally accessible signature for the quasi Bose-glass is the appearance of low-lying resonances and a suppression of the dominant resonance of the Mott-insulator phase.

Abstract— Octaphenyltetraanthraporphyrazinato palladium undergoes a self‐sensitized photoreaction in the presence of oxygen to form a substituted palladium phthalocyanine with four endoperoxide bridges. This compound exhibits photophysical behavior similiar to palladium tetra‐tert‐butyl‐phthalocyanine. The phthalocyanine‐palladium complex with four endoperoxide bridges ejects molecular oxygen when excited by consecutive two‐photon absorption in the Q‐band region at 662 nm. This photocyclo‐reversion, which produces palladium porphyrazines bearing a diminished number of endoperoxide bridges, can occur up to four times per initial molecule. Irradiation of these photoproducts in the presence of oxygen produces substituted palladium phthalocyanine containing four endoperoxide groups.