The photodynamics of bacteriorhodopsin were studied by transient absorption and gain measurements after excitation with femtosecond pulses at 620 nm. With probing pulses at longer wavelengths (A> 770 nm) the previously reported formation of the J intermediate (with a time constant of 500f 100 fs) was confirmed. With probing pulses around 700 nm, a faster process with a relaxation time of 200 rt...

We report a value for the D2-line frequency of K with 0.25 ppb uncertainty. The frequency is measured using an evacuated ring-cavity resonator whose length is calibrated against a reference laser. The D2 line presents a problem in identifying the line center because the closely-spaced energy levels of the excited state are not resolved. We use computer modelling of the measured spectrum to extr...

The class II masers of methanol are associated with the early stages of formation of high-mass stars. Modelling of these dense, dusty environments has demonstrated that pumping by infrared radiation can account for the observed masers. Collisions with other molecules in the ambient gas also play a significant role, but have not been well modelled in the past. Here we examine the effects on the ...

The exchange charge model of crystal field theory has been used to analyze the ground and excited state absorption of tetrahedrally coordinated Cr ion in lithium aluminum oxide LiAlO2 (γ-phase) and lithium dioxogallate LiGaO2. The parameters of the crystal field acting on the Cr ion are calculated from the crystal structure data, taking into account the crystal lattice ions located at distances...

Toxic reactants are a common result of the interaction of sunlight with pharmaceutical agents transported in the blood system or applied topically. Over the past decade there has been a considerable amount of research toward understanding both the unimolecular deactivation pathway of photoexcited pharmaceutical products and their photosensitizing capability in the presence of biological substra...

We report a series of quantum-chemical calculations for the ground and some of the low-lying excited states of an isolated LiYb molecule by the spin-orbit multistate complete active space second-order perturbation theory (SO-MS-CASPT2). Potential energy curves, spectroscopic constants, and transition dipole moments (TDMs) at both spin-free and spin-orbit levels are obtained. Large spin-orbit ef...

We present the first computer graphics algorithm designed to simulate the aurora, a natural phenomenon of great visual beauty and considerable scientific interest. The algorithm is based on the current understanding of the physical origin of this natural display. The aurorae are mainly caused by high-energy electrons originating in the sun and entering the earth’s atmosphere in narrow regions c...

When gaseous mercury is subjected to an electrical discharge, such as in a fluorescent light bulb, street lamp, or laboratory discharge tube, the collisions between the mercury atoms and the electrons are energetic enough to excite one of the 6s electrons to a higher energy state, while the remaining 79 electrons (including the other 6s electron) remain undisturbed. Depending upon which empty s...

We present results from transient absorption spectroscopy on a series of artificial light-harvesting dyads made up of a zinc phthalocyanine (Pc) covalently linked to carotenoids with 9, 10, or 11 conjugated carbon-carbon double bonds, referred to as dyads 1, 2, and 3, respectively. We assessed the energy transfer and excited-state deactivation pathways following excitation of the strongly allow...

Helium nanodroplet isolation is used to produce van der Waals-bound quartet state alkali trimers ~Na3 and K3! selectively over the corresponding chemically bound doublet trimers. Frequency-resolved excitation and emission spectroscopy reveals the presence of nonadiabatic spin–flip processes in the electronically excited states. A total of four quartet to quartet electronic transitions are obser...