Site Selective and Single Complex Laser-Based Spectroscopies: A Window on Excited State Electronic Structure, Excitation Energy Transfer, and Electron Phonon Coupling of Selected Photosynthetic Complexes Ryszard Jankowiak,* Mike Reppert, Valter Zazubovich, J€org Pieper, and Tonu Reinot Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, United States Department of Physics, Concordia University, Montreal H4B1R6 Quebec, Canada Max-Volmer-Laboratories for Biophysical Chemistry, Technical University of Berlin, Germany Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia

Site selective and single complex laser-based spectroscopies: a window on excited state electronic structure, excitation energy transfer, and electron-phonon coupling of selected photosynthetic complexes.

Coherent multidimensional vibrational spectroscopy (CMDVS) is an emerging field that offers new oportunities to probe specifically intramolecular and intermolecular interactions in complex samples with the improved resolution and selectivity expected of a multidimensional method. In particular, it provides structural and dynamical information about correlations between modes. It provides this information on the picosecond time scales characteristic of vibrational dephasing. CMDVS is based on the perturbations that are induced in a mode when other coupled modes are excited. It is the vibrational analogue to multidimensional nucler magnetic resonance (NMR). In this review, we present the background that led to the development of CMDVS, a brief summary of the different methods of non-linear laser spectroscopy and how they can achieve CMDVS, the relationships between CMDVS and multidimensional NMR, and the theory necessary to understand the experimental results. The experimental approaches reviewed fall into ...

Coherent multidimensional vibrational spectroscopy

Multiresonant coherent multidimensional spectroscopy is a frequency-domain method that uses tunable excitation pulses to excite multiple quantum coherences (MQCs) and/or state populations using fully coherent or partially coherent excitation pathways. Pairs of states that are coupled by intra- and intermolecular interactions re-emit light at their frequency differences. The MQCs are coherent and interfere constructively to create phase-matched output beams. Scanning the excitation frequencies with fixed-excitation-pulse time delays creates multidimensional spectra, whereas scanning the time delays with fixed excitation frequencies measures the MQCs’ coherent and incoherent dynamics. Multiresonant methods can excite any combination of vibrational and/or electronic states and use any coherence pathway. Cross-peaks occur between states when the excitation of one perturbs the other. This requirement for coupling acts to eliminate spectral congestion. Spectral resolution is increased because multiresonant meth...

Multiresonant coherent multidimensional spectroscopy.

Recent research has expanded the capabilities of four-wave mixing by providing it with component selectivity, site selectivity, and mode selectivity. The selectivity is achieved by taking advantage of the three resonance enhancements that occur in a four-wave mixing process. New spectral scanning strategies allow one to scan a single resonance while maintaining the other two resonances at constant values. The constant resonances can be used to select a specific component, a specific site within an inhomogeneously broadened envelope of a component, and/or a specific vibrational or vibronic mode of that site. The scanned resonance will then contain enhanced features corresponding to the particular component, site, and/or mode that was chosen by the constant resonances. These component and site selective capabilities of the four-wave mixing complement the single vibronic level fluorescence methods. The relative transition intensities from a specific component or site reflect the mode coupling betwee...

Molecular, multiresonant coherent four-wave mixing spectroscopy

A new family of selective four-wave mixing methods, based on the establishment of vibrational nonlinear polarizations with multiple resonances, is proposed. This family includes double-infrared resonances, vibrationally enhanced Raman resonance, and vibrationally enhanced two-photon resonance. These methods are related to traditional Raman and infrared spectroscopy, but the methods are shown to have the capabilities for component and conformer selectivity, line-narrowing of inhomogeneously broadened vibrational transitions, and mode selection. The theoretical foundations for the methods are developed and directed to possible applications.

Theoretical Foundations for a New Family of Infrared Four-Wave Mixing Spectroscopies

Inhomogeneous broadening typically interferes with the observation of sharp featured fluorescence from organic chromophores dispersed in glasses and polymers. Fluorescence line narrowing (FLN) and nonlinear spectroscopic techniques can be used to obtain site selective spectra in photochemically stable systems but produce ambiguous results when the incident laser induces frequency domain hole burning. The effects of hole burning on the observed line narrowed fluorescence signal are described by introducing a time-dependent site distribution

Scanned laser fluorescence line narrowing spectroscopy of photosensitive organic chromophores

Multiresonant nonlinear spectroscopy has been used to achieve narrowing of inhomo-geneously broadened spectral transitions. Multiply enhanced nonparametric spectroscopy(MENS) has been used to observe the narrowing in pentacene doped benzoic acid. The signaldependence of pentacene and benzoic acid lines on sample absorbance, detuning and laserintensity are studied.Recent papers from our group have established that nonlinear spectroscopy offersunique capabilities for dissecting individual spectral features of components in mixtures,narrowing inhomogeneously broadened spectral bands, and measuring mode mixing between vibrational states [1-22]. This paper will present additional information that complements previously published work. The reader is encouraged to consult the original literature for themain body of the work.Figure 1 shows schematic spectra for a molecular state gas phase that is either isolated in the gas phase, incorporated in a ______ L unique condensed phase environment, or distributed among

Bradford B. Price

Papers

Molecular, multiresonant coherent four-wave mixing spectroscopy

Scanned laser fluorescence line narrowing spectroscopy of photosensitive organic chromophores

Multiresonant nonlinear spectroscopy