The interaction between photosynthetic cofactors and the surrounding bath or proteinenvironment is addressed via experimental measurements of the optical coherenceresponses from bacteriochlorophylla (Bchla) chromophores within the photosyntheticreaction center (RC) of Rhodobacter sphaeroides and solutions of Bchla monomers inTHF and pyridine. The results indicate that both the spectrum of fluctuations andchromophore bath coupling strengths vary between solutions and protein. In particular,the protein environment yields faster dephasing, faster spectral diffusion, andsignificantly more inhomogeneity than solutions.

D. C. Arnett

L. D. Book

C. C. Moser

P. L. Dutton

N. F. Scherer

Electronic and VibrationalCoherence in PhotosyntheticCofactors: Comparisonof Solutions and Proteins

We have measured the femtosecond time-resolved absorption spectra of para-nitroanilinein acetonitrile just after the photoexcitation to the lowest excited singlet state. TheSingular Value Decomposition (SVD) analysis shows that two temporal evolutionsfollow the photoexcitation. The fast component (0.7 ps time constant) describes thedissociation of the 1:2 associated form to generate the 1:0 form followed by itsreassociation with AN molecules. A slower temporal evolution of 10 ps is most likely torepresent the cooling down process of the whole system.

K.  Mohanalingam

S.  Yamaguchi

H.  Hamaguchi

Two Distinct SolvatedStructures of Para-Nitroanilinein Acetonitrile and TheirDissociation and ReassociationDynamics

Line shape analysis based on resonance Raman spectra of HITCI is used to determinethe details of the vibrational part of the line broadening function. Forced LightScattering with 20 fs pulses from a Ti: sapphire laser measured optical dephasing probingwith an Ar+ laser. The observed response is well described by the line broadeningfunction derived from the fluorescence line shape.

A.  Kummrow

S. H. Ashworth

K.  Lenz

Resonance Raman and OpticalDephasing Study of Hitci

We perform femtosecond mid-infrared pump-probe spectroscopy on hydrogen-bondedethanol dissolved in CCl4. We find that upon excitation of the OH-stretching vibrationthe hydrogen bonds are predissociated on a femtosecond time scale, and that thepredissociation time constant depends strongly on the hydrogen-bond strength.

S.  Woutersen

U.  Emmerichs

H. J. Bakker

Femtosecond Mid-InfraredSpectroscopy ofHydrogen-Bonded Liquids

Time-resolved resonance Raman (TR3) and absorbance difference studies of the excitedstates of Cu(TPP) (TPP&#61;5,10,15,20-tetraphenylporphyrin) have been carried out with&#60; 10 ps times resolution in THF and pyridine solvents. In THF the distinctive transientRaman bands in the &#957;2 and &#957;4 regions, previously observed with ns laser pulses, grow inthe first 55 ps before decaying in 100&#39;s of ps. The &#8710;A spectra also show biphasic decay.This behaviour is associated with attack by solvent on the 4-coordinate excited state toform the longer lived species observed in TR3 experiments.In pyridine two component decay is also observed but it is the shorter-lived specieswhich gives the transient Raman bands seen previously with ns laser excitation. Thisstate is different from that seen in THF. At 5 ps delay &#957;4 is broader than in the groundstate and, more importantly, there is a significant shift in the two pyridine bands at ca.1000 cm-1. This implies a significant involvement of the pyridine-based orbitals in theexcited state.

S. E. J. Bell

J. H. Rice

J. J. McGarvey

R. E. Hester

J. N. Moore

R. N. Perutz

T.-Q.  Ye

Y.  Mizutani

T.  Kitagawa

Time-Resolved Resonance RamanSpectroscopy of Excited-StatePorphyrins

Radicals formed by one-electron oxidation of 4-aminoresorcinol have been studied asmodels for the active site free radical intermediate which forms as a stable productduring anaerobic incubation of amine oxidases with amine substrates. Pulse radiolysisshows that the radical undergoes ionisations with pKa&#39;s of 3.4 and 6.4. Although the twodeprotonated forms are difficult to distinguish by absorption spectroscopy, they haveclearly different resonance Raman spectra. Comparison with the resonance Ramanspectrum of the enzyme intermediate shows it to be the singly deprotonated form of theradical.

Roger H. Bisby

Steven A. Johnson

Anthony W. Parker

Susan M. Tavender

Time-Resolved Resonance RamanStudies of Radicals From4-Aminoresorcinol as Modelsfor the Active Site RadicalIntermediate in CopperAmine Oxidases

Ultrafast time-resolved visible-pump, far-IR (THz) probe spectroscopy has beendeveloped in our lab and has been applied to study carrier dynamics in photoexcitedGaAs and dipole solvation dynamics in betaine and p-nitroaniline. This type ofspectroscopy enables us to study for the first time the nonequilibrium interactionbetween excited electronic states and low frequency vibrational modes.

Richard  McElroy

Klaas  Wynne

Time-Resolved Terahertz Spectroscopy of Condensed Phase Reactions

Photoexcitation of internal proton transfer in the tinuvin molecule causes the excitationof some low frequency vibrational modes which oscillate with high amplitudes in acoherent manner over 700 fs. Such effect is observed for the first time applying two colorpump/probe measurement with 25 fs pulses. Based on resonance Raman spectra anormal coordinate analysis of the modes is performed. It is shown that the nuclearmovement given by the normal vibration of one of the modes serves to open up abarrierfree proton transfer path.

M.  Pfeiffer

C.  Chudoba

A.  Lau

T.  Elsaesser

Coherent Motion of LowFrequency Vibrations in UltrafastExcited State Proton Transfer

Cooling kinetics of trans-stilbene (tSB) photoexcited to a vibrationally excited state inthe first excited singlet (S1) manifold was studied with picosecond time-resolved Ramanspectroscopy. The observed cooling curves of S1tSB in chloroform (CHCI3) and inchloroform-d (CDCl3) were identical within the experimental uncertainties. For S1tSBin chloroform, there was no experimental evidence for strong intermolecular vibration-vibration(V&#8211;V) resonance energy transfer in the picosecond to sub-picosecond timeregion.

Koichi  Iwata

Hiro-o  Hamaguchi

Solute-Solvent Energy TransferAnd Cooling Kineticsof Photoexcited S1Trans-StilbeneProbed With Picosecond RamanSpectroscopy: ComparisonBetween Chloroform andChloroform-d Solutions

Single color pump-probe and photon-echo experiments have been performed on the COstretching mode of W(CO)6 at about 1983 cm-1 in various liquids and solidenvironments. Combined with absorption data, the measured T1 and T2 times suggestthe following conclusions: in all liquids studied, the IR absorption band ishomogeneously broadened, whereas, inhomogeneous broadening is observed in solidmatrices and in a xerogel. At low temperature, the echo decay is much faster in methanethan in argon host.

C.  Cr&#233;pin

M.  Broquier

H.  Dubost

D.  L&#39;hermite

A.  Tramer

J. P. Galaup

J. M. Berset

J. M. Ortega

Vibrational Dynamicsin Molecular Condensed PhasesWith The Clio Free Electron Laser

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Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Articles

Electronic and Vibrational Coherence in Photosynthetic Cofactors: Comparison of Solutions and Proteins

Two Distinct Solvated Structures of Para-Nitroaniline in Acetonitrile and Their Dissociation and Reassociation Dynamics

Resonance Raman and Optical Dephasing Study of Hitci

Femtosecond Mid-Infrared Spectroscopy of Hydrogen-Bonded Liquids

Time-Resolved Resonance Raman Spectroscopy of Excited-State Porphyrins

Time-Resolved Resonance Raman Studies of Radicals From 4-Aminoresorcinol as Models for the Active Site Radical Intermediate in Copper Amine Oxidases

Time-Resolved Terahertz Spectroscopy of Condensed Phase Reactions

Coherent Motion of Low Frequency Vibrations in Ultrafast Excited State Proton Transfer

Solute-Solvent Energy Transfer And Cooling Kinetics of Photoexcited S₁Trans-Stilbene Probed With Picosecond Raman Spectroscopy: Comparison Between Chloroform and Chloroform-d Solutions

Vibrational Dynamics in Molecular Condensed Phases With The Clio Free Electron Laser