A5027358802- Spectroscopy and Quantum Chemical Studies
- Photochemistry and Electron Transfer Studies
- Organic Electronics and Photovoltaics
- Advanced Chemical Physics Studies
- Spectroscopy Techniques in Biomedical and Chemical Research
- Photosynthetic Processes and Mechanisms
- Hemoglobin structure and function
- Quantum, superfluid, helium dynamics
- Conducting polymers and applications
- Spectroscopy and Laser Applications
- DNA and Nucleic Acid Chemistry
- Synthesis and Properties of Aromatic Compounds
- Fullerene Chemistry and Applications
- Organic Light-Emitting Diodes Research
- Nonlinear Optical Materials Research
- Perovskite Materials and Applications
- Free Radicals and Antioxidants
- Laser-Matter Interactions and Applications
- Photoreceptor and optogenetics research
- Spectroscopy and Chemometric Analyses
- Protein Structure and Dynamics
University of California, Los Angeles
2015-2020
Los Angeles City College
2018
University of Rochester
2012-2017
University of Pennsylvania
2013
Optica
2013
China Jiliang University
2012
Case Western Reserve University
2005-2007
4-(Dimethylamino)benzonitrile (DMABN) has been one of the most studied photoinduced charge-transfer (CT) compounds for over 50 years, but due to complexity its excited electronic states and importance both intramolecular solvent reorganization, detailed microscopic mechanism CT is still debated. In this work, we have probed ultrafast process DMABN in methanol using broad-band transient absorption spectroscopy from 280 620 nm ultraviolet femtosecond stimulated Raman (FSRS) incorporating a 330...
Photoinduction of long-lived polarons Photosynthetic complexes and organic photovoltaics can rapidly create separated charges upon photoexcitation. However, unproductive charge recombination often occurs in the human-made system. This is part because acceptor donor structures are much larger. Huber et al. created aqueous micelles that pair conjugated polyelectrolyte donors with fullerene acceptors at a smaller interface. They observed photoinduced formation polarons—stable pairs charges—with...
The first step of photosynthesis is the absorption light by antenna complexes. Recent studies light-harvesting complexes using two-dimensional electronic spectroscopy have revealed interesting coherent oscillations. Some contributions to those coherences are assigned coherence and therefore implications for theories energy transfer. To assign these femtosecond data gain insight into interplay among vibrational resonances, we need detailed information on vibrations in excited state compared...
It is generally presumed that the vast majority of carriers created by chemical doping semiconducting polymer films are coulombically trapped counteranion, with only a small fraction free and responsible for increased conductivity essential organic electronic applications. At higher levels, it also possible bipolarons to form, which expected be less conductive than single polarons. Unfortunately, there no simple way distinguish polarons, polarons using steady-state spectroscopy. Thus, in...
Abstract Molecular dopants are often added to semiconducting polymers improve electrical conductivity. However, the use of such does not always produce mobile charge carriers. In this work, ultrafast spectroscopy is used explore nature carriers created following doping conjugated push–pull with both F 4 TCNQ (2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane) and FeCl 3 . It shown that for one particular material, by entirely non‐conductive bipolarons single polarons, transient absorption...
The ultrafast dynamics of 2'-deoxyguanosine 5'-monophosphate after excitation with ultraviolet light has been studied femtosecond transient absorption (TA) and stimulated Raman spectroscopy (FSRS). TA kinetics anisotropy spectra reveal a rapid relaxation from the Franck-Condon region, producing an extremely red-shifted emission band at ∼440 nm that is formed 200 fs subsequent for 0.8-1.5 ps, consistent prior studies. Viscosity dependence shows initial relaxation, before 0.5 same in water or...
A scanning multichannel technique (SMT) has been implemented in femtosecond stimulated Raman spectroscopy (FSRS). By combining several FSRS spectra detected at slightly different positions of the spectrograph via SMT, we have eliminated systematic noise patterns (“fixed pattern noise”) due to variation sensitivity and characteristics individual charge-coupled device (CCD) pixels. In nonresonant FSRS, solvent subtraction can effectively remove even without SMT. However, case resonant show...
Femtosecond stimulated Raman spectroscopy (FSRS) has emerged as a powerful new technique that is capable of obtaining resonance spectra fluorescent species and transient photochemical intermediates. Unlike related infrared absorption techniques, the FSRS signal quite sensitive to laser power utilized in vibrational probing event. In particular, are highly intensity picosecond Raman‐pump pulse. We have measured dependence using pulse energies from ~10 −9 −5 J molecules with range molar...
The structure of the hydrated electron, particularly whether it exists primarily within a cavity or encompasses interior water molecules, has been subject much recent debate. In Paper I [C.-C. Zho et al., J. Chem. Phys. 147, 074503 (2017)], we found that mixed quantum/classical simulations with and non-cavity pseudopotentials gave different predictions for temperature dependence rate photoexcited electron's relaxation back to ground state. this paper, measure ultrafast transient absorption...
para-Nitroaniline (PNA) plays an essential role as the prototype model of push-pull chromophores. The nature and degree participation vibrational degrees freedom in charge-transfer internal-conversion processes are current issues great theoretical practical importance. Ultrafast time-resolved anti-Stokes resonance Raman spectroscopy (TRARRS) experiments on PNA dimethyl sulfoxide with three different excitation wavelengths were performed to probe these dynamical influences. dynamics...
A tunable, ultrafast (approximately 100 fs-approximately 1 ps) laser system generating mid-IR (3-10 microm) and UV/visible (392-417 nm, 785-835 nm) radiation is described its output characterized. The designed to explore vibrational dynamics in the condensed phase a direct, two-pulse, time-resolved manner, using Raman spectroscopy as probe. To produce resolution, probe pulses are spectrally narrowed by use of long doubling crystal. Frequency-resolved optical gating used evaluate beam...
The temporally overlapping, ultrafast electronic and vibrational dynamics of a model five-coordinate, high-spin heme in nominally isotropic solvent environment has been studied for the first time with three complementary techniques: transient absorption, time-resolved resonance Raman Stokes, anti-Stokes spectroscopies. Vibrational associated an evolving ground-state species dominate observations. Excitation into blue side Soret band led to very rapid S2 --> S1 decay (sub-100 fs), followed by...