Transient picosecond infrared (IR) spectra of the OH and NH-stretch (v&#61;0&#8211;1) absorptionbands of several hydrogen-bonded complexes have been investigated. Solutions of1:1 complexes of weak acids (methanol, triethylsilanol and pyrrole, &#60; 0.1 mol/dm3) andbases (acetonitrile, pyridine and tetrahydrofuran, &#60; 2 mol/dm3) in CCl4 at 295 K wereinterrogated with IR excitation and broadband probing. Lorentzian-shaped absorptionbands are uniformly bleached while those with near-Gaussian bandshapes producetransient spectral holes. These results indicate a base functionality and hydrogen-bondstrength dependence for determining the broadening mechanisms of these absorptions.

S. M. Arrivo

V. D. Kleiman

W. T. Grubbs

T. P. Dougherty

E. J. Heilweil

Infrared Spectral Hole Burningof 1:1 Hydrogen-Bonded Complexesin Solution

We present a theoretical description of the dynamics of vibrational wave packets in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>1</mml:mtext><mml:mi>g</mml:mi></mml:msub></mml:mrow></mml:math> state of Xe2. As an illustration, a simulation of a picosecond pump excitation-probeionization laser experiment is carried out. The initial wavepacket is calculated using anexplicit modelling of the short-pulse excitation process and propagated for up to160 picoseconds. Evidence of fractional and full revivals of the wavepacket has beenfound and analyzed. The time delayed ionization signal is simulated using first orderperturbation theory and shows clear oscillations corresponding to the temporaldevelopment of the wavepacket.

J. F. Castillo

K. L. Reid

A Theoretical Study of the
Dynamics of Vibrational Wave
Packets in the <svg style="vertical-align:-5.76988pt" height="18.1" version="1.1" viewBox="0 0 15.675 18.1" width="15.675" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,10.863)"><path id="x31" d="M384 0h-275v27q67 5 81.5 18.5t14.5 68.5v385q0 38 -7.5 47.5t-40.5 10.5l-48 2v24q85 15 178 52v-521q0 -55 14.5 -68.5t82.5 -18.5v-27z" /></g><g transform="matrix(.012,-0,0,-.012,8.225,14.938)"><path id="x1D454" d="M546 430q-14 -33 -37.5 -140t-38.5 -209q-29 -195 -156 -289q-29 -21 -70 -37t-78 -16q-62 0 -102.5 37t-40.5 69q0 27 26 48q19 15 25 -3q13 -43 46.5 -69t87.5 -26q55 0 83 21q29 22 50 65t43 140q14 64 29 163h-2q-55 -81 -149 -152q-59 -44 -102 -44q-23 0 -43.5 30&#xA;t-20.5 85q0 74 32.5 145.5t84.5 117.5q40 35 100 58.5t117 23.5q21 0 65 -8q30 -6 44 -6zM456 386q-40 16 -81 16q-29 0 -64 -13q-42 -17 -85 -97q-19 -36 -31.5 -86t-12.5 -86q0 -64 30 -64q20 0 52.5 21t60.5 52q74 81 95 123q26 62 36 134z" /></g></svg> State Of Xe2

Replacing the chromophore of bacteriorhodopsin with chemically modified retinalanalogs which cannot isomerize, allows to measure directly side effects from the laserpulse used for sample excitation in step-scan FT-IR measurements. Comparison withstatic temperature difference spectra and temperature-jump experiments shows that theobserved effects can mainly be attributed to heating of the sample by the laser pulse. Thesize of resulting spectral changes is compared to difference bands of the photoreaction.

C.  R&#246;dig

H.  Georg

F.  Siebert

I.  Rousso

M.  Sheves

Temperature Effects Of ExcitationLaser Pulses During Step-ScanFT-IR Measurements

Third- and fifth-order impulsive stimulated Raman scattering experiments are performedto study low-frequency intermolecular vibrations in CS2/pentane binary mixtures. Thechanges of the optical Kerr effect response cannot be assigned unequivocally to a singlemicroscopic process. In particular, the homogeneous and inhomogeneous line broadeningmechanisms cannot be determined. Temporally two-dimensional Raman scatteringexperiments indicate that the correlation time of fluctuations of the intermolecularpotential decreases upon dilution. The experimental results give evidence of strongcoupling between the ultrafast coherent vibrations and the slow reorientational diffusion.

Thomas  Steffen

Satoru  Nakashima

Koos  Duppen

Temporally Two-DimensionalFifth-Order Raman Scatteringon Intermolecular Vibrationsin Cs2/Pentane Binary Mixtures

Via intense ps-excitation of the OH-stretching vibration of ethanol diluted in CCl4 wesucceed in spectral hole burning within the inhomogeneously broadened oligomer band.The lifetime of the transient hole and the v&#61;1-level of the OH-stetch of associatedethanol molecules are determined to be about 1.2 and 1.7 ps, respectively. Furtherdynamical features are discussed which give evidence for energy migration within theH-bonded ethanol chains and subsequent breaking of the oligomers into shorterfragments.

R.  Laenen

C.  Rauscher

Spectral Hole Burning andEvidence for Vibrational EnergyMigration of H-Bonded MoleculesObserved With Transient InfraredSpectroscopy

Exciplex formation dynamics of photoexcited copper(II) tetrakis (4-N-methylpyridyl)porphyrin (Cu(II)(TMpy-P4)) with added poly(dA-dT)2 and poly(dG-dC)2 has beeninvestigated by using femtosecond transient absorption and nanosecond and picosecondtransient Raman spectroscopic methods. It was observed that the decay time constant ofthe exciplex is strongly dependent on the polynucleotide and has a strong correlationwith the appearance of new transient Raman bands.

Sae Chae Jeoung

Hyo Soon Eom

Dongho  Kim

Transient Absorption and RamanStudies on Exciplex FormationDynamics of PhotoexcitedCu(II)(TMpy-P4) With SyntheticPolynucleotide

For coordination compounds containing CO or CN groups, fast time-resolved infraredspectroscopy (TRIR) provides a convenient method of probing excited states andintermediates. TRIR has proved particularly powerful for probing the structure andkinetics of organometallic intermediates. The interpretation is particularly straightforwardwhen combined with IR data from matrix isolation experiments, although therecan be some subtle differences. In excited state studies, shifts in &#957;(CO) and &#957;(CN)frequencies, from ground to excited state, are sensitive to the changes in electrondistribution on excitation, thus allowing the distinction between charge-transfer andnon-charge-transfer transitions. Subtle effects on excited state &#957;(CO) band positionsoccur with change from fluid to rigid solvent-&#8220;infrared rigidochromism&#8221;. There is oftena change in &#957;(CO) band width on excitation; this can be interpreted in terms of specificinteractions between the excited species and the solvent. This paper presents some of ourrecent work in this area.

J. J. Turner

M. W. George

I. P. Clark

I. G. Virrels

Excited States and Intermediatesby Time-Resolved InfraredSpectroscopy

The S0, T1 and S1 Raman spectra of bacteriochlorophyll a, bacteriopheophytin a andchlorophyll a were recorded for the species of natural abundance isotopic compositionand those of totally substituted with 15N, 13C and 2H isotopes. Based on empiricalassignments of the Raman lines, changes in the bond orders in the macrocycle upontriplet and singlet excitation are discussed.

Yasushi  Koyama

Leenawaty  Limantara

Tokutake  Sashima

Transient Raman Spectroscopyof Isotope-Substituted Speciesof Bacteriochlorophyll a,Bacteriopheophytin a AndChlorophyll a: Changes in theBond Orders in the MacrocyclesUpon Triplet and SingletExcitation

The serine proteinase mechanism has been studied using a wide range of techniques overmany years and is now well understood in terms of the formal chemical changes thatoccur on the reaction pathway. At the atomic level our understanding is less secure inthat available techniques are unable to define interactions such as hydrogen bondingwith sufficient accuracy. Atomic interaction is strongly dependent upon separationdistances and these need to be measured either directly or indirectly in the dynamicreacting system. Infrared spectroscopy has been applied to the study of chymotrypsinacylenzyme reaction intermediates with the aim of measuring, albeit indirectly, thestrength of hydrogen bonding in the oxyanion hole catalytic device. These measurementshave been successful with moderately specific substrates but there is a long way to go interms of improved time-resolution. It is tentatively proposed that tetrahedralintermediates accumulate at high pH. This is, we believe, the first report of the relativelydirect observation of this phenomenon in any reacting ester system, chemical or enzymic.The approach used with the serine proteinases has been applied to studies of thetranspeptidase of Streptococcus pneumoniae PBP2x. We have shown that the acylenzymeformed from benzylpenicillin hydrogen bonds most strongly in the oxyanion hole. Thisbonding, in contrast to serine proteinases and &#946;-lactamases where the interactionfacilitates catalysis, serves to stabilise the ester intermediate as required for effectiveantibiotic action. We see this as a good example of &#8216;Nature knows Best&#8217; since semisyntheticantibiotics, designed to be resistant to hydrolysis by &#946;-lactamases, hydrogenbond more weakly and the acylenzymes hydrolyse more rapidly.

C. W. Wharton

M. G. P. Page

R. S. Chittock

T. E. Regan

S.  Ward

Infrared Spectroscopy of EnzymeReaction Intermediates

Ultrafast visible and infrared polarization spectroscopy has been used to reveal theorientation of donor and acceptor molecules in the intermolecular electron transferbetween coumarin 337 and dimethylaniline.

Boris  Akhremitchev

Chengfei  Wang

Gilbert C. Walker

Ultrafast Infrared and VisibleSpectroscopy of IntermolecularElectron Transfer From DimethylAniline to Coumarin 337

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Laser Chemistry | Hindawi

Laser Chemistry

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Papers are published upon acceptance, regardless of the Special Issue publication date.

Laser Chemistry

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Articles

Infrared Spectral Hole Burning of 1:1 Hydrogen-Bonded Complexes in Solution

A Theoretical Study of the Dynamics of Vibrational Wave Packets in the State Of Xe₂

Temperature Effects Of Excitation Laser Pulses During Step-Scan FT-IR Measurements

Temporally Two-Dimensional Fifth-Order Raman Scattering on Intermolecular Vibrations in Cs₂/Pentane Binary Mixtures

Spectral Hole Burning and Evidence for Vibrational Energy Migration of H-Bonded Molecules Observed With Transient Infrared Spectroscopy

Transient Absorption and Raman Studies on Exciplex Formation Dynamics of Photoexcited Cu(II)(TMpy-P4) With Synthetic Polynucleotide

Excited States and Intermediates by Time-Resolved Infrared Spectroscopy

Transient Raman Spectroscopy of Isotope-Substituted Species of Bacteriochlorophyll a, Bacteriopheophytin a And Chlorophyll a: Changes in the Bond Orders in the Macrocycles Upon Triplet and Singlet Excitation

Infrared Spectroscopy of Enzyme Reaction Intermediates

Ultrafast Infrared and Visible Spectroscopy of Intermolecular Electron Transfer From Dimethyl Aniline to Coumarin 337

Laser Chemistry

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Articles

Infrared Spectral Hole Burning of 1:1 Hydrogen-Bonded Complexes in Solution

A Theoretical Study of the Dynamics of Vibrational Wave Packets in the State Of Xe2

Temperature Effects Of Excitation Laser Pulses During Step-Scan FT-IR Measurements

Temporally Two-Dimensional Fifth-Order Raman Scattering on Intermolecular Vibrations in Cs2/Pentane Binary Mixtures

Spectral Hole Burning and Evidence for Vibrational Energy Migration of H-Bonded Molecules Observed With Transient Infrared Spectroscopy

Transient Absorption and Raman Studies on Exciplex Formation Dynamics of Photoexcited Cu(II)(TMpy-P4) With Synthetic Polynucleotide

Excited States and Intermediates by Time-Resolved Infrared Spectroscopy

Transient Raman Spectroscopy of Isotope-Substituted Species of Bacteriochlorophyll a, Bacteriopheophytin a And Chlorophyll a: Changes in the Bond Orders in the Macrocycles Upon Triplet and Singlet Excitation

Infrared Spectroscopy of Enzyme Reaction Intermediates

Ultrafast Infrared and Visible Spectroscopy of Intermolecular Electron Transfer From Dimethyl Aniline to Coumarin 337

A Theoretical Study of the Dynamics of Vibrational Wave Packets in the State Of Xe₂

Temporally Two-Dimensional Fifth-Order Raman Scattering on Intermolecular Vibrations in Cs₂/Pentane Binary Mixtures