The photosynthetic reaction center of Rb. sphaeroides is investigated by unique pump-probeanisotropy methods using 13 fs optical pulses tunable throughout the near IRabsorption band. The time and wavelength resolved pump probe anisotropy transientsyield detailed experimental descriptions of the energy levels, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:msup><mml:mtext>y</mml:mtext><mml:mtext>+</mml:mtext></mml:msup></mml:mrow></mml:msub></mml:mrow></mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:msup><mml:mtext>y</mml:mtext><mml:mtext>-</mml:mtext></mml:msup></mml:mrow></mml:msub></mml:mrow></mml:math> of theexcitonically coupled special pair (P), and dynamics prior to charge separation,particularly energy transfer from the accessory bacteriochlorophylla&#39;s (B) to the specialpair (P).

D. C. Arnett

C. C. Moser

P. L. Dutton

N. F. Scherer

Pump Probe Anisotropy Studiesof the PhotosyntheticReaction Center

Transient resonance Raman (TR2) spectroscopy has been used to investigate the metalligandcharge-transfer (MLCT) excited states of Ru(II) polypyridyl complexes inDNAandin homogeneous solution. In DNA, complexes of the type [Ru(L)2(L&#8242;)]2+ were studied,where L&#61;2, 2&#8217;-bipyridyl (bpy), 1,4, 5, 8-tetraazaphenanthrene (tap), and L&#8242; dipyrido[3,2:a-2&#8242; ,3&#8242;:c]-phenazine (dppz) or 1,4,5,8,9,12-hexaazatriphenylene (HAT). For[Ru(bpy)2(HAT)]2+, the enhancement pattern of vibrational modes in the TR2 spectraattributable to reduced <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>HAT</mml:mtext></mml:mrow><mml:mrow><mml:mo>&#x22C5;</mml:mo><mml:mo>&#x2212;</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> in the triplet MLCT state suggest perturbations to theintraligand transition of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>HAT</mml:mtext></mml:mrow><mml:mrow><mml:mo>&#x22C5;</mml:mo><mml:mo>&#x2212;</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math> in the presence of DNA. Transient RR spectra for[Ru(tap)2(dppz)]2+ are indicative of formation of the species RunII(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mtext>tap</mml:mtext></mml:mrow><mml:mrow><mml:mo>&#x22C5;</mml:mo><mml:mo>&#x2212;</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>)(tap)(dppz) byelectron transfer from DNA to the triplet MLCT state of the complex.TR2 spectra for complexes of the type, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msup><mml:mrow><mml:mrow><mml:mo>[</mml:mo><mml:mrow><mml:msub><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mtext>Ru</mml:mtext><mml:msub><mml:mrow><mml:mrow><mml:mo>(</mml:mo><mml:mrow><mml:mtext>bpy</mml:mtext></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mi>n</mml:mi></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:mtext>L</mml:mtext><mml:mo>)</mml:mo></mml:mrow></mml:mrow><mml:mo>]</mml:mo></mml:mrow></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>, n&#61;1, 2 where L&#61;a triazolebridging ligand, illustrate the use of the technique as a probe of the response of MLCTstates to the electronic environment.

Colin G. Coates

John J. McGarvey

Steven E. J. Bell

Luc  Jacquet

John M. Kelly

Tia  Keyes

Johannes G. Vos

Transient Resonance RamanStudies of Ru(II) Complexes in DNAand in Homogeneous Media

When a protein finds its native three-dimensional structure from the unstructuredamino-acid chain various processes spanning a large time range are relevant. Tounderstand the mechanism of protein folding one needs to cover the entire folding/refolding (U&#8596;N) reaction on a structural level. In the case of RNase A, the mainstructural changes occur in the ms time range, that can be monitored with rapid-scan-FTIR spectroscopy combined with rapid mixing techniques. To induce unfolding weinject aqueous protein solution into a hot IR cuvette and record the time course of thespectral changes. A lag phase is found when the unfolding conditions are relatively weak,suggesting an unfolding intermediate.

H.  Georg

C. W. Wharton

F.  Siebert

Temperature Induced ProteinUnfolding and Folding of RNasea Studied by Time-ResolvedInfrared Spectroscopy

We have been studying the excited state spectra of several molecules related toelectroluminescent conducting polymers. The excited state structure corresponds to theconducting state in these systems. We have obtained data on 1,4-bis(2,2&#8242;-methylstyryl)-benzene (2MSB) as a model system of poly (P-phenylenevinylene) (PPV). We observeboth sharp and broad features in the spectra. The sharp bands occur at a constant energyshift relative to the probe wavelength. We attribute the sharp bands to resonance Ramanbands of the S1 state of 2MSB. We assign the broad band at &#8764;740 nm to resonanceemission between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>S</mml:mtext><mml:mi>n</mml:mi></mml:msub></mml:mrow></mml:math> and S1. We believe that this is the first observation of resonancesecondary radiation (RSR) between two electronically excited states in a large molecule.

Terry L. Gustafson

James D. Leonard

Picosecond Transient Raman
Spectra of S1 Bis(Methylstyryl)-
Benzene: Observation of S1&#x2190;<svg style="vertical-align:-3.3907pt" height="15.65" version="1.1" viewBox="0 0 14.775 15.65" width="14.775" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(.017,-0,0,-.017,.062,11.362)"><path id="x53" d="M409 504l-29 -5q-16 60 -44.5 96t-86.5 36q-54 0 -82.5 -32t-28.5 -77q0 -51 30.5 -82.5t96.5 -65.5l35.5 -18t33 -19.5t33.5 -23.5l27 -25.5t24.5 -32t13.5 -36.5t6 -45q0 -80 -62 -134.5t-160 -54.5q-47 0 -98 15q-22 7 -50 21q-8 23 -27 155l30 7q7 -27 18 -52&#xA;t30 -51.5t49 -42.5t67 -16q56 0 88 32.5t32 87.5q0 51 -31.5 82t-98.5 67q-80 44 -110 73q-55 53 -55 124q0 75 56 126.5t150 51.5q53 0 126 -23z" /></g><g transform="matrix(.012,-0,0,-.012,8.125,15.45)"><path id="x1D45B" d="M495 86q-46 -47 -87 -72.5t-63 -25.5q-43 0 -16 107l49 210q7 34 8 50.5t-3 21t-13 4.5q-35 0 -109.5 -72.5t-115.5 -140.5q-21 -75 -38 -159q-50 -10 -76 -21l-6 8l84 340q8 35 -4 35q-17 0 -67 -46l-15 26q44 44 85.5 70.5t64.5 26.5q35 0 10 -103l-24 -98h2&#xA;q42 56 97 103.5t96 71.5q46 26 74 26q9 0 16 -2.5t14 -11.5t9.5 -24.5t-1 -44t-13.5 -68.5q-30 -117 -47 -200q-4 -19 -3.5 -25t6.5 -6q21 0 70 48z" /></g></svg> Resonance Emission

A picosecond optical parametric amplifier, OPA, system suitable for pump and probespectroscopy has been developed. Two OPAs are simultaneously pumped by a titaniumsapphire regenerative amplifier to produce several microjoules output over the 470 to2000 nm wavelength range. One OPA used as the probe operates with c. 25 cm-1linewidth over this tuning range. The system is optimised for TR3 spectroscopy. Somepreliminary experiments on Trolox, a water soluable Vitamin E derivative, are presented.

M.  Towrie

G.  Gaborel

P.  Matousek

A. W. Parker

W.  Shaikh

R. H. Bisby

Tunable Picosecond OpticalParametric Amplifiers for TimeResolved Resonance RamanSpectroscopy

Femtosecond VIS-pump-IR-probe experiments (time resolution: 300fs, detectableabsorption change: 5.10-5 , frequency range: 1000&#8211;1800 cm-1) were applied to theultrafast photo isomerisation of azobenzene and the protonated Schiff base of retinal.The energy of the pump photon heats the vibrational system of the molecule, leading topronounced anharmonic frequency shifts which are dominated by the anharmoniccoupling between the investigated high frequency modes to hot low frequency modes. Amodel taking into account this intramolecular anharmonicity and assuming a welldefined intramolecular temperature gives a good fit of the experimental data.

P.  Hamm

S.  Ohline

M.  Zurek

T.  R&#246;schinger

Vibrational Cooling After PhotoIsomerisation: First Applicationof a Novel IntramolecularThermometer

Anthony W. Parker

Preface

The vibrational relaxation lifetimes of the CO stretching mode of Cr(CO)6 and Mo(CO)6adsorbed in the cage of the HY, DY and NaY-type zeolites were measured at varioustemperature by pump-probe method using picosecond infrared laser pulses. It wasshown by comparing the lifetimes that the accepting modes include both the vibrationalmodes of the metal carbonyl and those associated with the cations on the zeolite surface.The analysis of the temperature dependence of the lifetimes revealed that the number ofthe excited accepting modes are four with their energy lying around 500 cm-1.

Ken  Onda

Michio  Yaginuma

Akihide  Wada

Kazunari  Domen

Chiaki  Hirose

Vibrational Relaxation Processof Polyatomic MoleculesAdsorbed in Zeolites

The electronic absorption spectrum of the bithiophene radical cation prepared by&#947;-irradiation in a glassy Freon matrix is presented, together with the Raman spectraexcited at 550 and 425 nm, in resonance with the two absorption bands. The 425 nmexcited Raman spectrum was also recorded in a room temperature acetonitrile solution,in this case the radical cation was generated via a photoinduced electron transferreaction. The resonance Raman spectra were interpreted with the help of densityfunctional theory calculations. The results indicate the existence of at least two rotamersof the bithiophene radical cation. The time-domain method was applied to thesimultaneous fitting of the absorption and resonance Raman spectra.

T.  Keszthelyi

M. M.-L. Grage

R.  Wilbrandt

C.  Svendsen

O. S. Mortensen

The Radical Cation of Bithiophene:An Experimental and TheoreticalStudy

Microsecond and picosecond time-resolved infrared studies of Ru(PPh3)3(CO)(H)2 havedemonstrated that reductive elimination of H2 is complete within 5 ps of UV photolysis.

M. G. Colombo

M. W. George

J.  N. Moore

D. I. Pattison

R. N. Perutz

I. G. Virrels

T.-Q.  Ye

Ultrafast Photodissociation ofHydrogen From Ru(PPh3)3(CO)(H)2:A Time-Resolved Infrared Study

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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

Pump Probe Anisotropy Studies of the Photosynthetic Reaction Center

Transient Resonance Raman Studies of Ru(II) Complexes in DNA and in Homogeneous Media

Temperature Induced Protein Unfolding and Folding of RNase a Studied by Time-Resolved Infrared Spectroscopy

Picosecond Transient Raman Spectra of S₁ Bis(Methylstyryl)- Benzene: Observation of S₁← Resonance Emission

Tunable Picosecond Optical Parametric Amplifiers for Time Resolved Resonance Raman Spectroscopy

Vibrational Cooling After Photo Isomerisation: First Application of a Novel Intramolecular Thermometer

Preface

Vibrational Relaxation Process of Polyatomic Molecules Adsorbed in Zeolites

The Radical Cation of Bithiophene: An Experimental and Theoretical Study

Ultrafast Photodissociation of Hydrogen From Ru(PPh₃)₃(CO)(H)₂: A Time-Resolved Infrared Study

Laser Chemistry

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Proceedings of the Eighth Conference on Time-Resolved Vibrational Spectroscopy

Articles

Pump Probe Anisotropy Studies of the Photosynthetic Reaction Center

Transient Resonance Raman Studies of Ru(II) Complexes in DNA and in Homogeneous Media

Temperature Induced Protein Unfolding and Folding of RNase a Studied by Time-Resolved Infrared Spectroscopy

Picosecond Transient Raman Spectra of S1 Bis(Methylstyryl)- Benzene: Observation of S1← Resonance Emission

Tunable Picosecond Optical Parametric Amplifiers for Time Resolved Resonance Raman Spectroscopy

Vibrational Cooling After Photo Isomerisation: First Application of a Novel Intramolecular Thermometer

Preface

Vibrational Relaxation Process of Polyatomic Molecules Adsorbed in Zeolites

The Radical Cation of Bithiophene: An Experimental and Theoretical Study

Ultrafast Photodissociation of Hydrogen From Ru(PPh3)3(CO)(H)2: A Time-Resolved Infrared Study

Picosecond Transient Raman Spectra of S₁ Bis(Methylstyryl)- Benzene: Observation of S₁← Resonance Emission

Ultrafast Photodissociation of Hydrogen From Ru(PPh₃)₃(CO)(H)₂: A Time-Resolved Infrared Study