Two-pulse second-order interferometric autocorrelation responses of single Ag nanoparticles are reported. The surface plasmon-enhanced second harmonic generation interferogram for single Ag colloids shows significant broadening with respect to the laser pulse second-order autocorrelation. The interferometric autocorrelation response is described and analyzed with a density matrix formalism that incorporates (phenomenologically) the population and the polarization relaxation of the surface plasmon. The total dephasing time (T 2 ) of the surface plasmon in single Ag colloids is determined to be 10 fs. The present results are compared to previously reported values obtained from ensemble studies of Ag particles and from the line width of the absorption spectrum. Extension of the present ultrafast measurements, the first performed on single nanoparticles, to single molecules studies is discussed.

The relaxation dynamics of excess electrons in a water jet between 5 and 70°C have been investigated on an ultrashort timescale. We have probed the transient absorption of the system immediately after W multiphoton-ionization with a 266 nm ultrashort laser pulse and a time resolution of about 50 fs. Robe wavelengths ranging from 450 to loo0 nm have been provided by a generated white-light continuum. The data suggest a superposition of geminate recombination of the solvated electrons with their original counter-ions and of relaxation into thermal equilibrium. Relaxation into thermal equilibrium is the much faster process and is completed after about 6 ps while the geminate recombination is much slower, temperature independenL and prevails for at least loops. The here postulated interpretation of the data clearly shows that no other transient states than "hot solvated electrons" are required for an understanding of the observed ultrafast dynamics within our time resolution.

A diphenylphosphine functionalized benzoic acid was applied for the synthesis of a homoleptic dimolybdenum-based metalloligand, exhibiting four symmetrically placed phosphine donor sites. This allowed subsequent treatment with gold(I), rhodium(I), and iridium(I) precursors to obtain early-late heterometallic complexes as well as Lewis acid-base adducts with BH. The compounds were in-depth investigated by spectroscopic techniques, single-crystal X-ray diffraction, and femtosecond laser spectroscopy. The coordination of different metal fragments to the dimolybdenum metalloligand leads to a fine-tuning of the system's optical properties, which correlates well with fluorescence quantum yield measurements. Nevertheless, triplet dynamics still remain the dominating channel in these systems with an intersystem crossing time constant below 1 ps.

N,N‐dimethylaminobenzophenone (DMABP) represents an intramolecular donor–π–acceptor system resulting in luminescent properties that are highly sensitive to the local surrounding due to twisted intramolecular charge transfer (TICT). In this study, DMABP was covalently linked to a single (ss) or double‐stranded (ds) DNA and studied by a combination of UV/Vis absorption and fluorescence spectroscopy as well as femtosecond pump–probe measurements. As a result of embedding DMABP into a DNA environment, a drastic increase of the fluorescence quantum yield (QY) by a factor of more than 100 was detected, as further evidenced by an increase of the lifetime of the relevant excited states from less than 10 ps to more than 100 ps. A direct comparison between the ss‐ and ds‐DNA systems further demonstrates the high sensitivity to the surrounding area by means of a two‐fold difference in QY and fluorescence lifetimes. As a consequence, the respective DNA moiety (stacking and folding knot) affects significantly the competition between radiationless relaxation processes and fluorescence by interacting with DMABP.

The prompt transfer of cutting-edge science into students’ curricula is a challenging task. Often research experiments are too complex or expensive to be translated into a secondary or tertiary education setting. Herein, we introduce a laboratory experiment that translates the recently developed research technique of a wavelength dependent, photochemical action plot into a student accessible format. The practical incorporates aspects of photophysics, required to calculate a constant photon emission from each different colored LED, as well as polymer chemistry in understanding the mechanism and quantitatively determining the polymerization conversion. During this practical the students (i) learn about areas where photochemical reactions are used to generate everyday materials, (ii) understand and apply the concepts of absorption and Beer–Lambert’s law, (iii) record and evaluate a photochemical action plot, and (iv) critically discuss the disparate nature of action and absorption spectra to generate an understanding of the implications for photochemical material design.