Multidimensional Vibrational Spectroscopy Research Articles

Spectroscopic Characteristics of Triply Vibrationally Enhanced Four-Wave Mixing Spectroscopy

Triply vibrationally enhanced (TRIVE) four-wave mixing is a fully resonant, frequency domain spectroscopy that is capable of coherent multidimensional vibrational spectroscopy. TRIVE has 12 different coherence pathways that differ in their time ordering and resonances. The pathways are the coherent analogue to two-color pump−probe pathways. Specific pathways or sets of pathways can be chosen by appropriate selection of time delays and resonance conditions. The pathways have characteristic positions and line shapes in three-dimensional frequency space and their coherent interference has consequences in interpreting the spectra. The line shapes and the relative intensities of different pathways are dependent on the population relaxation and dephasing rates. The different pathways also have different capabilities for line-narrowing inhomogeneously broadened transitions. The narrowing is controlled by the interference between pathways and the quantum level interference between different parts of the inhomogen...

Vibrational correlations via coherent multi-resonant four-wave mixing

A new family of coherent multidimensional vibrational spectroscopies has been developed which provide opportunities for establishing the correlations between vibrational modes that result from intra- and intermolecular interactions. The multidimensional spectroscopies contain cross-peaks between the modes because of coupling where the oscillations from one mode affect the optical properties of other modes. This paper presents an experimental overview of representative methods for coherent multidimensional vibrational spectroscopy.

Experimental Determinations of Coherent Multidimensional Vibrational Spectroscopy

Coherent multidimensional vibrational spectroscopy is a new technique for establishing correlations between features in vibrational spectra that are caused by intra- and intermolecular interactions. These interactions cause cross-peaks between vibrational transitions that reflect the coupling. In this paper, we use Doubly Vibrationally Enhanced Infrared Spectroscopy (DOVE-IR) and DOVE-Raman processes to obtain coherent two dimensional vibrational spectra. The spectra are fitted to obtain the dephasing rates and third order susceptibilities <TEX>$(χ^{(3)})$</TEX> for the nonlinear processes. We show that the DOVE <TEX>$χ^{(3)}$</TEX> values are directly related to the molar absorptivities and Raman <TEX>$χ^{(3)}$</TEX>. We then use these relationships to obtain estimates for the <TEX>$χ^{(3)}$</TEX> of the stimulated photon echo and <TEX>$χ^{(5)}$</TEX> of the six wave mixing spectroscopies, respectively. We also predict the ratio of the cascaded four wave mixing signal to the six wave mixing signal.

Correlated line broadening in multidimensional vibrational spectroscopy

The third-order optical response of two coupled anharmonic vibrations interacting with a Brownian oscillator bath that induces energy level fluctuations with arbitrary time scales and degree of correlation is calculated. Two-dimensional correlation plots show distinct signatures of these fluctuations in the various possible three pulse, infrared, femtosecond techniques.

Femtochemistry and femtobiology: the new age.

A review is given of the advances in femtochem. and their importance in the study of biol. systems. These advances include the multidimensional vibrational spectroscopies and the time-resolved structural techniques. [on SciFinder (R)]

Magnetic Resonance Analogies in Multidimensional Vibrational Spectroscopy

Abstract We survey the principles for the design of multidimensional vibrational spectroscopies that draw upon the analogy with liquid or solid state NMR and EPR spectroscopy. The much faster time-scales and the different energy regime in laser spectroscopy provide additional possibilities that lack magnetic spectroscopy counterparts. We also discuss the notion of through-bond vs through-space couplings between localized vibrations, which are of different nature than in NMR.

Coherent multidimensional vibrational spectroscopy

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 three main classes: non-degenerate four-wave mixing which is doubly vibrationally enhanced, degenerate four-wave mixing which is triply vibrationally enhanced and six-wave mixing which has three Raman transitions. CMDVS has been implemented in both the time domain and the frequency domain. Finally, the review describes possible extensions of CMDVS and speculates on its future.

Multi-dimensional vibrational spectroscopy measured from different phase-matching conditions

We developed a theoretical method that can systematically treat the phase-matching condition of nonlinear infrared or Raman measurements. This method might be a rational tool for the analysis of observed signals from various directions based on the response function especially under non-impulsive excitation. Model calculations of the third-order nonlinear IR spectroscopy for a Brownian harmonic oscillator system are performed. We discuss the variation of signals that depend on the observation direction and the temporal width of excitation pulse in comparison with the behavior within the impulsive limit approximation.

Three-Dimensional Spectroscopy of Vibrational Energy Relaxation in Liquid Methanol

Vibrational energy relaxation (VER) of neat methanol at ambient temperature is studied with a three-dimensional vibrational spectroscopy technique. The first two dimensions are represented by a time series of incoherent anti-Stokes Raman spectra at a given mid-IR pump frequency. The third dimension involves changing the mid-IR pump frequency within the manifold of CH and OH stretching transitions ν(CH) and ν(OH). Each 2D representation shows the VER dynamics occurring as a result of pumping a specific vibrational transition. The decay of the pumped transition into first-generation daughters, and the subsequent decay into second-, and even third-generation daughters can be monitored. The third dimension shows how VER depends on the nature of the pumped transition. Additional information about the buildup of excitation in the bath of lower-energy collective excitations (phonons) is obtained by monitoring the heating of CCl4 spectators in methanol−CCl4 mixtures. Three distinct stages are seen in VER of ν(CH). The pumped ν(CH) creates two quanta of bending vibrations δ(CH) or δ(OH) (0−1 ps), the δ(CH) vibrations preferentially create CO stretch ν(CO), and the δ(OH) create methyl rock ρ(CH3) (2−5 ps), and then ρ(CH3) and ν(CO) decay into phonons (5−15 ps). Three stages are also seen in ν(OH) VER except that the first stage involves exciting every other vibration to some extent. About 10% of ν(OH) decay occurs in four stages, where the first stage is ν(OH) → ν(CH). The IR−Raman 3D technique is compared to other multidimensional vibrational spectroscopies. This 3D method is presently the most powerful technique for studying VER in condensed phases. It is sensitive to overtone and combination transitions buried under more intense fundamental absorption spectra. In addition it is sensitive to very weak cascaded anharmonic couplings responsible for the excitation of successive generations of daughter vibrations.