Nonlinear vibrational spectroscopy

Wright J C, Labuda M J, Zilian A, Chen P C and Hamilton J P 1997 New selective nonlinear vibrational spectroscopies J. Luminesc. 72-74 799-801... 

Vidal F, Busson B, Six C, Tadjeddine A, Dreesen L, Humbert C, Peremans A, Thiry P. 2004. Methanol dissociative adsorption on Pt(lOO) as studied by nonlinear vibrational spectroscopy. J Electroanal Chem 563 9-14. 

If ultrafast nonlinear vibrational spectroscopy [1-3] has recently developed into an important tool providing original informations on the dynamics of weak hydrogen bonds (H-bonds), the simpler linear infrared (IR) vs(X—H) absorption spectroscopy spectra remains, however, to be an important method for the understanding of this dynamics. Considerable experimental and theoretical works have been done in this last field [4—17]. 

Nonlinear vibrational spectroscopy provides accessibility to a range of vibrational information that is hardly obtainable from conventional linear spectroscopy. Recent progress in the pulsed laser technology has made the nonlinear Raman effect a widely applicable analytical method. In this chapter, two types of nonlinear Raman techniques, hyper-Raman scattering (HRS) spectroscopy and time-frequency two-dimensional broadband coherent anti-Stokes Raman scattering (2D-CARS) spectroscopy, are applied for characterizing carbon nanomaterials. The former is used as an alternative for IR spectroscopy. The latter is useful for studying dynamics of nanomaterials. 

In a similar manner, one can also consider third-order nonlinear vibrational spectroscopy. CARS is one of well-known third-order nonlinear optical phenomena... 

To address this gap in understanding, the surface specific nonlinear vibrational spectroscopy, sum frequency generation (SFG) has been applied to study the hexagonal ice surface, Ih. The Ih crystalline form is chosen as the focus of this work because it is the stable form of ice for ambient conditions on Earth. Further, the most abundant exposed face is the hexagonal or basal face. The second most abundant face consists of the cylinder sides, also called the prism face. This work examines both of these common faces. 

The interaction with the fluctuating surrounding leads to an additional broadening of the individual lines by vibrational dephasing [22-25]. Nonlinear vibrational spectroscopy allows one to separate the different couplings in the nonlinear time-resolved response following femtosecond vibrational excitation. In particular, the coherent vibrational dynamics can be isolated from processes of population relaxation [26[ and energy redistribution. 

Coherent Anti-Stokes—Raman Scattering Ab initio calculations of nonlinear vibrational spectroscopies is a field that is very much in its infancy, and we will therefore not dwell much on this topic here, Umiting ourselves to a recent example from our own research group, namely the foiu -wave mixing processes that lead to CARS [290]. 

Fig. 6.10 Setup for IR pump/SFG probe, time-resolved nonlinear vibrational spectroscopy. Reprinted with permission from Morin et al. (1992). Copyright 1992, American Institute of Physics.

Because of the generality of the symmetry principle that underlies the nonlinear optical spectroscopy of surfaces and interfaces, the approach has found application to a remarkably wide range of material systems. These include not only the conventional case of solid surfaces in ultrahigh vacuum, but also gas/solid, liquid/solid, gas/liquid and liquid/liquid interfaces. The infonnation attainable from the measurements ranges from adsorbate coverage and orientation to interface vibrational and electronic spectroscopy to surface dynamics on the femtosecond time scale. 

The compound can also be made by photolysis of a mixture of CIF and O3 in Ar at 4-15 K evidence for the expected nonlinear by structure comes from vibration spectroscopy (Fig. 17.26a). 

Hyper-Raman spectroscopy is not a surface-specific technique while SFG vibrational spectroscopy can selectively probe surfaces and interfaces, although both methods are based on the second-order nonlinear process. The vibrational SFG is a combination process of IR absorption and Raman scattering and, hence, only accessible to IR/Raman-active modes, which appear only in non-centrosymmetric molecules. Conversely, the hyper-Raman process does not require such broken centrosymmetry. Energy diagrams for IR, Raman, hyper-Raman, and vibrational SFG processes are summarized in Figure 5.17. 

Cho M, Hess C, Bonn M. 2002. Lateral interactions between adsorbed molecules Investigations of CO on Ru(OOl) using nonlinear surface vibrational spectroscopies. Phys Rev B 65 ... 

In order to realize molecular-vibration spectroscopy, coherent anti-Stokes Raman scattering (CARS) spectroscopy is employed, which is one of the most widely used nonlinear Raman spectroscopes (Shen 1984). CARS spectroscopy uses three incident fields including a pump field (< i), a Stokes field (0)2, 0 2 < 1) and a probe field (<0/ = <0i), and induces a nonlinear polarization at the frequency of <03 = 2<0i - <02 which is given in a scalar form by... 

In this chapter, we showed the capability of near-field optical spectroscopy combined with vibrational spectroscopy and nonlinear optics for biochemical applications. The evanescent field localized at the nanoscale tip realized the extremely small light source for various spectroscopes in the near-field. Especially when the tip is made... 

Ultrafast vibrational spectroscopy offers a variety of techniques for unraveling the microsopic dynamics of hydrogen bonds occurring in the femto- to picosecond time domain. In particular, different vibrational couplings can be separated in nonlinear experiments by measuring vibrational dynamics in real-time. Both coherent vibrational polarizations and processes of population and energy relaxation have been studied for a number of hydrogen bonded systems in liquids [1],... 

To date, a number of chemically selective near-field imaging methods have been demonstrated. Near-field contrast mechanisms that rely on electronic spectroscopy (UV-visible absorption and fluorescence),204 vibrational spectroscopy (IR absorption and Raman spectroscopies), dielectric spectroscopy (microwave dispersion), and nonlinear spectroscopy (second harmonic generation) have all been demonstrated at length scales well below the diffraction limit of light. 

In our discussion the usual Born-Oppenheimer (BO) approximation will be employed. This means that we assume a standard partition of the effective Hamiltonian into an electronic and a nuclear part, as well as the factorization of the solute wavefunction into an electronic and a nuclear component. As will be clear soon, the corresponding electronic problem is the main source of specificities of QM continuum models, due to the nonlinearity of the effective electronic Hamiltonian of the solute. The QM nuclear problem, whose solution gives information on solvent effects on the nuclear structure (geometry) and properties, has less specific aspects, with respect the case of the isolated molecules. In fact, once the proper potential energy surfaces are obtained from the solution of the electronic problem, such a problem can be solved using the standard methods and approximations (mechanical harmonicity, and anharmonicity of various order) used for isolated molecules. The QM nuclear problem is mainly connected with the vibrational properties of the nuclei and the corresponding spectroscopic observables, and it will be considered in more detail in the contributions in the book dedicated to the vibrational spectroscopies (IR/Raman). This contribution will be focused on the QM electronic problem. 

Kim et al. [22] have used vibrational sum-frequency generation spectroscopy (SFG) to characterize the surfaces of (3-HMX single crystals, as well as the interface between HMX and the copolymer Estane. SFG is a nonlinear vibrational spectroscopic technique, related to optical parametric amplification that selectively probes vibrational transitions at surfaces and interfaces. Compared with bulk HMX, the surface vibrational features are blueshifted and observed splittings are larger. The technique may have application to detection of explosive residues on surfaces. 

In this section we present theoretical and experimental demonstrations of a vibrational spectroscopic technique, vibrational echo spectroscopy (VES) (54,55). The VES technique can generate a vibrational transition spectrum with background suppression using the nonlinear vibrational echo pulse sequence. In contrast to the previous results, VES is a utilization of vibrational echoes to measure spectra rather than dynamics. In a standard vibrational echo experiment, the wavelength of the IR light is fixed, and the delay, r, between the excitation pulses is scanned. In VES, r is fixed and the wavelength is scanned. 

We shall conclude this chapter with a few speculative remarks on possible future developments of nonlinear IR spectroscopy on peptides and proteins. Up to now, we have demonstrated a detailed relationship between the known structure of a few model peptides and the excitonic system of coupled amide I vibrations and have proven the correctness of the excitonic coupling model (at least in principle). We have demonstrated two realizations of 2D-IR spectroscopy a frequency domain (incoherent) technique (Section IV.C) and a form of semi-impulsive method (Section IV.E), which from the experimental viewpoint is extremely simple. Other 2D methods, proposed recently by Mukamel and coworkers (47), would not pose any additional experimental difficulty. In the case of NMR, time domain Fourier transform (FT) methods have proven to be more sensitive by far as a result of the multiplex advantage, which compensates for the small population differences of spin transitions at room temperature. It was recently demonstrated that FT methods are just as advantageous in the infrared regime, although one has to measure electric fields rather than intensities, which cannot be done directly by an electric field detector but requires heterodyned echoes or spectral interferometry (146). Future work will have to explore which experimental technique is most powerful and reliable. 

In recent years there has been significant interest in the extension of nonlinear optical spectroscopy to higher orders involving multiple time and/or frequency variables. The development of these multidimensional techniques is motivated by the desire to probe the microscopic details of a system that are obscured by the ensemble averaging inherent in linear spectroscopy. Much of the recent work to extend time domain vibrational spectroscopy to higher dimensionality has involved the use of nonresonant Raman-based techniques. The use of Raman techniques has followed directly from the rapid advancements in ultrafast laser technology for the visible and near-IR portions of the spectrum. Time domain nonresonant Raman spectroscopy provides access to an extremely... 

Venturo VA, Felker PM. Nonlinear Raman spectroscopy of ground-state intermolecular vibrations in benzene complexes. J Phys Chem 1993 97 4882-4886. 

Multidimentional nonlinear infrared spectroscopy is used for identification of dynamic structures in liquids and conformational dynamics of molecules, peptides and, in principle, small proteins in solution (Asplund et al., 2000 and references herein). This spectroscopy incorporates the ability to control the responses of particular vibrational transitions depending on their couplings to one another. Two and three-pulse IR photon echo techniques were used to eliminate the inhomogeneous broadening in the IR spectrum. In the third-order IR echo methods, three phase-locked IR pulses with wave vectors kb k2, and k3 are focused on the sample at time intervals. The IR photon echo eventually emitted and the complex 2D IR spectrum is obtained with the use of Fourier transformation. The method was applied to the examination of vibrational properties of N-methyl acetamid and a dipeptide, acyl-proline-NH2.in D20. The 2D IR spectrum showed peaks at 1,610 and 1, 670 cm 1, the two frequencies ofthe acyl-proline dipeptide. Geometry and time-ordering of the incoming pulse sequence in fifth-order 2D spectroscopy is shown in Fig. 1.3. 

Dr. Rohlfing s research interests include the experimental characterization of transient molecules relevant to combustion processes, linear and nonlinear laser spectroscopies, trace detection of pollutants, molecular beam and mass spectrometric studies of carbon and metal clusters, and vibrational relaxation dynamics. He is the author of approximately 50 peer-reviewed articles, holds membership in the American Chemical Society and the American Physical Society, and is a fellow of the American Association for the Advancement of Science. 

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