Spectroscopy picosecond laser

Noguchi, H., Yoda, E., Ishizawa, N., Kondo, J. N., Wada, A., Kobayashi, H. and Domen, K. (2005) Direct observation of unstable intermediate species in the reaction of trans-2-butene on ferrierite zeolite by picosecond infrared laser spectroscopy. J. Phys. Chem B, 109, 17217-17223. 

K. Berndt, H. Duerr and D. Palme, Picosecond laser spectroscopy with avalanche photodiodes, in Time Resolved Laser Spectroscopy in Biochemistry (J. R. Lakawicz, ed.), Proc. SPIE 909, 209-215... 

When molecules absorb a photon and produce an electronic excited state, the energy can be dissipated in several ways luminescence, radiationless decay to the ground state, and photochemistry. Luminescence dominated the older literature because it was easy to observe. A good review of luminescence is in Volume 3 of David Dolphin s seven-volume series The Porphyrins. Picosecond laser spectroscopy allowed for exploration of the radiationless decay pathways, particularly the initial steps that compete with luminescence and lead to photochemistry. Two principal forms of radiationless decay lead to long-term metastables ligand ejection and electron transfer. 

An intense femtosecond laser spectroscopy-based research focusing on the fast relaxation processes of excited electrons in nanoparticles has started in the past decade. The electron dynamics and non-linear optical properties of nanoparticles in colloidal solutions [1], thin films [2] and glasses [3] have been studied in the femto- and picosecond time scales. Most work has been done with noble metal nanoparticles Au, Ag and Cu, providing information about the electron-electron and electron-phonon coupling [4] or coherent phenomenon [5], A large surface-to-volume ratio of the particle gives a possibility to investigate the surface/interface processes. 

G. Gerber In our time-resolved experiments on the NaafZ ) state we observe the symmetric stretch even for long delay times. From nanosecond laser and CW laser spectroscopy it is well known that the B state does not decay on femtosecond or picosecond time scales. So I do not see how the decay in the picosecond experiment by Prof. Woste can be understood and how the evolution of the B state symmetric stretch into the pseudorotation and the radial motion can occur. 

Platinum porphyrin complexes can be prepared by reaction with PtCl2(PhCN)2. Purification of the final complex is by medium pressure liquid chromatography on alumina. The strongly phosphorescent platinum(II) porphyrin complexes are efficient sensitizers for stilbene isomerization. The quantum yields for the cis to trans process are greater than unity because of a quantum chain process in which the metalloporphyrin serves both as an energy donor and an acceptor.1110 Picosecond laser spectroscopy has been used to obtain time-resolved excited-state spectra of platinum octaethylporphyrin complexes, and to probe the excited-state energy levels.1111 Tetrabenzoporphyrin complexes have been prepared for platinum in both the divalent and tetravalent oxidation states. The divalent complex shows strong phosphorescence at 745 nm.1112... 

Video Imaging Systems in Picosecond Laser Spectroscopy... 

Picosecond laser spectroscopy has also been used to investigate the behaviour of 1,8-dichloroanthraquinone (DCAQ) upon irradiation in the presence of 2,5-dime thy lhexa-... 

The current detailed understanding of photo-induced electron transfer processes has been advanced dramatically by the development of modern spectroscopic methods. For example, the application of time-resolved optical spectroscopy has developed from modest beginnings (flash-phyotolysis with millisecond resolution) [108,109] to the current state of the art, where laser spectroscopy with nanosecond resolution [110-113] must be considered routine, and where picosecond [114-116] or even femtosecond resolution [117] is no longer uncommon. Other spectroscopic techniques that have been applied to the study of electron transfer processes include time-resolved Raman spectroscopy [118], (time resolved) electron spin... 

This narrative echoes the themes addressed in our recent review on the properties of uncommon solvent anions. We do not pretend to be comprehensive or inclusive, as the literature on electron solvation is vast and rapidly expanding. This increase is cnrrently driven by ultrafast laser spectroscopy studies of electron injection and relaxation dynamics (see Chap. 2), and by gas phase studies of anion clusters by photoelectron and IR spectroscopy. Despite the great importance of the solvated/ hydrated electron for radiation chemistry (as this species is a common reducing agent in radiolysis of liquids and solids), pulse radiolysis studies of solvated electrons are becoming less frequent perhaps due to the insufficient time resolution of the method (picoseconds) as compared to state-of-the-art laser studies (time resolution to 5 fs ). The welcome exceptions are the recent spectroscopic and kinetic studies of hydrated electrons in supercriticaF and supercooled water. As the theoretical models for high-temperature hydrated electrons and the reaction mechanisms for these species are still rmder debate, we will exclude such extreme conditions from this review. 

Luminescence measurements have been made on 2,5-distrylpyrazine and l,4-bis-( 3-pyridyl-2-vinyl)benzene in mixed crystals between 8 and 300 K. Solvent and pH dependences of the fluorescence spectra of 9-phenanthrylamine have been used to determine pK values. Picosecond and nanosecond laser spectroscopy have been used to study the photoenolization of 2-methylbenzo-phenone. ... 

Picosecond laser spectroscopy of 4 - ( 9-anthyryl)-hi, N-dimethylaniline and related compounds in various solvents indicates multiple excited states with different degrees of charge... 

Photocyclization of bis(9-anthryl)methane (67) and the corresponding photocycloreversion were shown by picosecond laser spectroscopy to have a common intermediate whose electronic structure is different in polar or nonpolar solvents as judged by different absorption spectra in various solvents (Manring et al., 1985). 

The substitution at the 1,4-position (compared to the usual 2-substitution as in 2-C1 or 2-isopropyl thioxanthone) of the thioxanthone skeleton (10.50) has a larger effect. Interactions with amines are rather complex on the picosecond timescale [159]. Photolysis under steady-state conditions as well as nanosecond laser spectroscopy suggests a possible mechanism for a C-Cl bond breaking. 

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