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The femtosecond fluorescence up-conversion technique is used for analyzing the ultrafast studies of solvation and intramolecular configurational dynamics of large-sized fluorophores in liquid solutions. The application of ultrafast processes can facilitate the in-depth study of the mechanism of molecular relaxation of large-sized molecules.

Research has been conducted on the cyclometalated Pt(thpy)(CO)(Cl) monomers where thpy is 2-(2'-thienylpyridinate). The emitting triplet state of these monomers has been investigated via the use of the optically detected magnetic resonance spectroscopy and high-resolution optical spectroscopy and the results are reported.

Research has been conducted on the Pd(qol) (sub)2 that has been dissolved in an n-octane matrix. The application of several spectroscopic methods at liquid helium temperatures is described.

Stationary and time-resolved studies for 9,10,19,20-tetramethylporphycene and 9,10,19,20-tetra-n-propylporphycene in condensed phases are performed to understand the coexistence of trans and cis tautomeric forms. The tautomerization coordinate which includes not only hydrogen translocation but also large-amplitude twisting of the two protonated pyrrole moieties attached to the opposite sides of the ethylene bridge confirms the excited state deactivation in porphycene and explains the existence of conical intersection along the single hydrogen transfer path leading from the trans to a high energy cis-2 tautomeric form.

Ultra absorption bleach recovery and fluorescence upconversion measurements performed for three CdSe samples with nanoparticle diameters of 2.7, 2.9 and 4.3 nm. The two types of experiments provides complementary information regarding the contributions of the different processes involved in the fast relaxation of electrons and holes in the CdSe quantum dots.

Results of a femtosecond fluorescence upconversion study of the C3-symmetrical disk molecular TAB (1a) and the subgroup molecule DAC (2a) are presented. The results show that 1a and 2a exhibit excited-state intramolecular double proton transfer (ESIDPT) with a typical time of approximately 200-300 fs in 1a, ESIDPT takes place for the molecule in the aggregated as well as the nonaggregated state.

Two papers were reported that focused on the nature and properties of the photo excited porphyrin triplet states in zinc porphyrin solid films, and were studied by using fluorescence detected magnetic resonance (FDMR). The zinc tetraphenylporphyrin (ZnTPP) films contain only a single, ligand, triplet species with zero-field splitting (ZFS) parameters very similar to those of ligated zinc tetra-(p-octylphenyl)-porphyrin (ZnTOPP).

Reports on a classical molecular dynamics simulations of the solvation dynamics of a strongly polar dye molecule in a weakly polar solvent. Compatibility of solvation times and amplitudes; Several differences in the solvation dynamics relative to the case of strong polar solvents; Lesser importance of the inertial component of the Stokes shift.

We have performed ultrafast absorption bleach recovery and fluorescence upconversion measurements ( approximately 100 fs time resolution) for three CdSe samples, with nanoparticle diameters of 2.7, 2.9, and 4.3 nm. The two types of experiments provide complementary information regarding the contributions of the different processes involved in the fast relaxation of electrons and holes in the CdSe quantum dots. Transient absorption and emission experiments were conducted for the 1S [1Se-1S3/2(h)] transition, 1S(e) and 1S3/2(h) representing the lowest electron (e) and hole (h) levels. The bleach recovery of the 1S transition shows a approximately 400-500 fs initial rise, which is followed by a size-dependent approximately 10-90 ps decay and finally a long-lived (approximately ns) decay. The fluorescence upconversion signal for the 1S transition shows quite different temporal behavior: a two times slower rise time (approximately 700-1000 fs) and, when the fluorescence upconversion signal has risen to about 20% of its maximum intensity, the signal displays a slight leveling off (bend), followed by a continued rise until the maximum intensity is reached. This bend is well reproducible and power and concentration independent. Simulations show that the bend in the rise is caused by a very fast decay component with a typical time of about 230-430 fs. Considering that the 1S quantum dot excitation is comprised of five exciton substates (F=+/-2, +/-1L, 0L, +/-1U, and 0U), we attribute the disparity in the rise of the bleaching and emission transients to the results from the dynamics of the different excitons involved in respectively the bleaching and fluorescence experiments. More specifically, in transient absorption, population changes of the F=+/-1U excitons are probed, in emission population effects for the F=+/-2 ("dark") and the F=+/-1L ("bright") exciton states are monitored. It is discussed that the fast (approximately 400-500 fs) rise of the bleach recovery is representative of the feeding of the F=+/-1U exciton (by filling of the 1S(e) electron level) and that the slower (approximately 700-1000 fs) feeding of the emissive +/-2, +/-1L excitons is determined by the relaxation of the hole levels within the 1S3/2 fine structure. Finally, the approximately 230-430 fs component, typical of the bend in the fluorescence transient, is attributed to the thermalization of the close-lying +/-2 ("dark") and +/-1L ("bright") excitons.