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12 pags., 7 figs., 1 tab., The time-resolved photodynamics of the methyl iodide cation (CH3I+) are investigated by means of femtosecond XUV-IR pump-probe spectroscopy. A time-delay-compensated XUV monochromator is employed to isolate a specific harmonic, the 9th harmonic of the fundamental 800 nm (13.95 eV, 88.89 nm), which is used as a pump pulse to prepare the cation in several electronic states. A time-delayed IR probe pulse is used to probe the dissociative dynamics on the first excited state potential energy surface. Photoelectrons and photofragment ions - and I+ - are detected by velocity map imaging. The experimental results are complemented with high level ab initio calculations for the potential energy curves of the electronic states of CH3I+ as well as with full dimension on-the-fly trajectory calculations on the first electronically excited state, considering the presence of the IR pulse. The and I+ pump-probe transients reflect the role of the IR pulse in controlling the photodynamics of CH3I+ in the state, mainly through the coupling to the ground state and to the excited state manifold. Oscillatory features are observed and attributed to a vibrational wave packet prepared in the state. The IR probe pulse induces a coupling between electronic states leading to a slow depletion of fragments after the cation is transferred to the ground states and an enhancement of I+ fragments by absorption of IR photons yielding dissociative photoionization., MLMS acknowledges financial support through a predoctoral contract from Universidad Complutense de Madrid (Spain) and FULMATEN-CM project funded by Madrid Regional Government under programme Y2018/NMT-5028. GR thanks the Netherlands Organization for Scientific Research (NWO) for financial support (Rubicon 68-50-1410). This project has received funding (SMP) from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie Grant agreement No. 842539 (ATTO-CONTROL) and has been financed in part by the Spanish State Research Agency (AEI/10.13039/501100011033), Grants PGC2018-096444-B-I00, PID2019-106125GB-I00 and PID2019-106732GB-I00, and the Madrid Regional Government through the program Proyectos Sin´ergicos de I + D (Grant Y2018/NMT-5028 FULMATEN-CM). FM acknowledges support from the ‘Severo Ochoa’ Programme for Centres of Excellence in R & D (SEV-2016-0686) and the ‘María de Maeztu’ Programme for Units of Excellence in R & D (CEX2018-000805-M). All calculations were performed at the Mare Nostrum Supercomputer of the Red Española de Supercomputacion (BSC-RES) and the Centro de Computaci ´ on´ Científica de la Universidad Autonoma de Madrid (CCC-UAM). MV and OK acknowledge the support ´ from the Deutsche Forschungsgeminschaft (KO 4920/1-1). This work was performed in the Max Born Institut (Berlin) in the kHz Laboratory and received financial support from LaserLab Europe through the MBI002239 project.

[EN] We report on UV-visible absorption and emission and ultrafast emission dynamics of 7-hydroxyquinoline (7HQ) encapsulated within titania-doped silicates (mesoporous and unstructured) and purely TiO2 nanomaterials. When titania is incorporated as larger (similar to 50 angstrom) nanoparticles (TiO2-MCM41), the stationary spectra and fluorescence decay times are very similar to those of the regular MCM-41 sample (R-MCM41). In turn, the presence of titania domains in MCM-41(Ti-MCM41) leads to a large increase of the ground state population of anionic (A) and zwitterionic (Z) forms of the adsorbed dye. This is explained in terms of the cooperative effect of Ti-OH groups and the MCM-41 framework interacting with the confined structures. The emission spectra in Ti-MCM41 show a partial fluorescence quenching, whereas a complete quenching occurs when the dye is interacting with pure TiO2 materials (mesoporous TiMeso and nonporous P25). A femtosecond emission study revealed a very short lifetime (10-14 ps) of the Z form. This strong emission quenching is assigned to an electron transfer process from the excited dye to the conduction band of TiO2 material. For 7HQ caged within TiMeso pores, this process occurs in 0.1-0.4 and 0.8-1.2 Ps for A and Z forms, respectively. However, for 7HQ/Ti-MCM41, the emission decays become longer (0.3-5 ps). This result is due to the presence of mixed dynamics gated from 7HQ molecules located close to and far from TiO2 domains, reflecting the heterogeneity of the sample and the competition between proton- and electron-transfer processes. Our results suggest negligible contribution of a direct titania excitation in the observed dynamics of the used materials., This work was supported by the MICINN through projects: Consolider Ingenio 2010 (CSD2009-0050, MULTICAT), MAT2008-01609, MAT2011-25472, MAT2009-14528-C02-01, and CTQ2010-17988 (PPQ subprogram). We thank Mr. Mikko Ojala for his help at the early stage of this work.

We report on studies of the recently synthesized compound (TPC1) with a promising potential use in dye-sensitized solar cells. We used steady-state as well as femtosecond (fs) to nanosecond (ns) time-resolved emission techniques to understand its behaviour under different conditions of solvation and light excitation. In polar solvents the equilibrium between TPC1 normal and anion structures was found to depend on solvent H-bond acceptor ability and concentration of the dye. We observed a correlation between the contribution of the normal form in the total absorption spectrum and solar energy conversion efficiency of the photovoltaic devices prepared in different baths, which are high in dichloromethane and low in tetrahydrofurane. Both forms exhibit a large charge transfer character in the excited state manifested by a large Stokes shift between absorption and emission maxima (up to 9000 cm(-1) in acetonitrile). The lifetime of the relaxed state of the normal structure varies significantly with the solvent polarity (from 80 ps in acetonitrile to 1.8 ns in n-hexane), and it is considerably shorter than that of the anion one (1.2-2.6 ns). The ultrafast relaxation processes are dominated by the solvation dynamics which is the fastest in acetonitrile (below 1 ps) and the slowest in ethanol (about 25 ps, the amplitude-averaged time). The results reported here should be relevant to a better understanding of the photobehaviour of metal-free dyes for solar cells and help in the design of new and more efficient dyes for conversion of light to electricity. QC 20110204

Using sub-5fs visible laser pulses, ultrafast time-resolved absorption change was observed for RuII (TPP)(CO) (TPP=5,10, 15, 20 tetraphenylporphirine) solved in chloroform. Exponential fitting of the time traces estimated decay life times of intermediates as 230±70 fs, 1150±260 fs, 2150±360 fs, and ≫4.8 ps for 1Qx(1,0)/(π,π∗),1Qx(0,0)(π,π∗), 3(d,π∗), and 3(π,π∗), respectively. Real-time 4.8 change of instantaneous molecular vibration frequency was studied by spectrogram analysis, which reflects gradual vibration mode change in the intersystem crossing from singlet state to triplet state.