Coherent x-ray Raman spectroscopy: a nonlinear local probe for electronic excitations

Nonlinear x-ray four-wave mixing experiments are becoming feasible due to rapid advances in high harmonic generation and synchrotron radiation coherent x-ray sources. By tuning the difference of two x-ray frequencies across the valence excitations, it is possible to probe the entire manifold of molecular electronic excitations. We show that the wave vector and frequency profiles of this x-ray analogue of coherent Raman spectroscopy provide an excellent real-space probe that carries most valuable structural and dynamical information, not available from spontaneous Raman techniques.     

Conical-wave nonlinear optics: From Raman conversion to extreme UV generation

Conical waves (CW) are a particular class of wavepackets that exhibit the notable feature of being stationary solutions for both linear and nonlinear propagation equations. The possibility of independently tuning the phase and group velocities of a CW is a unique feature that opens the possibility of a number of applications, in particular, we shall consider frequency conversion processes and divide the discussion into two parts: group velocity (GV)-matched and phase-matched nonlinear processes. As a GV-matched process, we consider stimulated raman scattering within optical filaments and we highlight the role of cross-phase modulation in the formation of GV-matched X-wave pulses, leading to high Raman conversion efficiencies and the formation of 15-fs compressed pulses. Conical waves, in particular, pulsed-Bessel beams, are then considered for phase-matching higher-order harmonic generation in the extreme UV region.     

Statistical methods in nonlinear dynamics

Sensitivity to initial conditions in nonlinear dynamical systems leads to exponential divergence of trajectories that are initially arbitrarily close, and hence to unpredictability. Statistical methods have been found to be helpful in extracting useful information about such systems. In this paper, we review briefly some statistical methods employed in the study of deterministic and stochastic dynamical systems. These include power spectral analysis and aliasing, extreme value statistics and order statistics, recurrence time statistics, the characterization of intermittency in the Sinai disorder problem, random walk analysis of diffusion in the chaotic pendulum, and long-range correlations in stochastic sequences of symbols.     

Recent Advances in linear and nonlinear Raman spectroscopy I

Raman spectroscopy has advanced considerably in the last several years due to rapid developments in instrumentation and the availability of theoretical methods for accurate calculation of Raman spectra, thus enormously facilitating the interpretation of Raman data. This review is restricted to cover papers mainly published in the Journal of Raman Spectroscopy, which serve to give a fast overview of recent advances in this research field as well as to provide readers of this journal a quick introduction to the various subfields of Raman spectroscopy. It also reflects the current research interests of the Raman community. Similar reviews of highly active areas of Raman spectroscopy will appear in future issues of this journal. Copyright © 2007 John Wiley & Sons, Ltd.     

Recent advances in linear and nonlinear Raman spectroscopy II

Following the first review on recent advances in linear and nonlinear Raman spectroscopy, the present review summarizes papers mainly published in the Journal of Raman Spectroscopy during 2007. This serves to give a fast overview of recent advances in this research field as well as to provide readers of this journal a quick introduction to the various subfields of Raman spectroscopy. It also reflects the current research interests of the Raman community. Similar reviews of highly active areas of Raman spectroscopy will appear in future issues of this journal. Copyright © 2008 John Wiley & Sons, Ltd.     

Reorientation dynamics in liquid alcohols from Raman spectroscopy

Polarized Raman spectroscopy has been employed to study the reorientational, or more specifically the translational relaxation dynamics, of alcohol molecules in pure liquids and aqueous solutions. It is found from the spectral width measurements that alcohol molecules in pure liquids have typically translational relaxation times on the order of picoseconds, following the order methanol < ethanol < i‐propanol < n‐propanol. Temperature‐dependent measurements show that hydrogen‐bonding (HB) and hydrophobic interactions control the translational motion. The hydrophobic interaction reduces the relaxation time more apparently in view of the  CH₃ group than the skeleton motion. For alcohol–water mixtures, the increase of water concentration generally slows down the relaxation process in a non‐monotonic behavior. However, the trend stops at a certain point and the motion of alcohol molecules becomes faster when the alcohol concentration further drops. Different mechanisms have been proposed to interpret these observations, which might be helpful to gain deeper insight into the HB networks of alcohols with water. Our study strongly illustrates that Raman spectroscopy can be applied to the study of fast translational motion of molecules in HB systems. Copyright © 2011 John Wiley & Sons, Ltd.     

Magnetocrystalline symmetry, spin statics and dynamics in high-temperature superconductors

The symmetry analysis of the magnetic structures of La₂CuO₄ and YBa₂Cu₃O_6+δ (δ 0.4) antiferromagnetic oxide has been carried out. The spin configurations and spin-reorientation transition fields have been found. The frequencies of uniform spin oscillations and the external field dependence of their polarization properties have been calculated. It has been shown that the spin excitation branches may include exchange modes among which some dipole-active modes can be present. The spectrum of the inelastic light scattering accompanied with the excitation of spin and libration (tilting) freedom degrees has been discussed.     

Recent advances in linear and nonlinear Raman spectroscopy. Part IV

The purpose of the review is to provide a concise overview of recent advances in the broadly defined field of Raman spectroscopy as reflected in part by the many articles published each year in the Journal of Raman Spectroscopy (JRS) as well as in trends across all related journals publishing in this research area. Context for the review is provided by considering statistical data on citations for the Thompson Reuters ISI Web of Science by year and by subfield of Raman spectroscopy. Additional statistics of number of papers and posters presented by category at the XXII International Conference on Raman Spectroscopy (ICORS 2010) is also provided. Papers published in JRS in 2009, as reviewed here, reflect trends at the cutting edge of Raman spectroscopy which is expanding rapidly as a sensitive photonic probe of matter at the molecular level with an ever widening sphere of novel applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Recent advances in linear and nonlinear Raman spectroscopy. Part V

The purpose of the review is to provide a concise overview of recent advances in the broadly defined field of Raman spectroscopy as reflected in part by the many articles published each year in JRS as well as in trends across all related journals publishing in this research area. Context for this review is derived from statistical data on article counts obtained from Thomson Reuters ISI Web of Knowledge by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations featuring Raman spectroscopy presented at the meetings of the Federation of Analytical Chemistry and Spectroscopy Societies 2011 and the Sixth International Conference on Advanced Vibrational Spectroscopy 2011. Papers published in JRS in 2010, as reviewed here, reflect trends at the cutting edge of Raman spectroscopy, which is expanding rapidly as a sensitive photonic probe of matter at the molecular level with an ever‐widening sphere of novel applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Recent advances in linear and nonlinear Raman spectroscopy. Part VII

The aim of this paper is to provide an overview of advances in the field of Raman spectroscopy as reflected in articles published each year in the Journal of Raman Spectroscopy as well as in trends across related journals publishing in this research area. The context for this review is derived from statistical data on article counts obtained from Thomson Reuters ISI Web of Knowledge by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations featuring Raman spectroscopy presented at the International Conference on Advanced Vibrational Spectroscopy in Kobe Japan in August 2013 and at SCIX 2013 sponsored by the Federation of Analytical Chemistry and Spectroscopy Societies in Milwaukee, Wisconsin, USA, October 2013. Papers published in the Journal of Raman Spectroscopy in 2012 are highlighted in this review and reflect topics and advances at the frontier of Raman spectroscopy, a field that is expanding rapidly as a sensitive photonic probe of matter at the molecular level in an ever widening sphere of novel applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Recent advances in linear and nonlinear Raman spectroscopy. Part VI

The purpose of this review is to provide a concise overview of recent advances in the broadly defined field of Raman spectroscopy as reflected in part by the many articles published each year in Journal of Raman Spectroscopy as well as in trends across all related journals publishing in this research area. Context for this review is derived from statistical data on article counts obtained from Thomson Reuters ISI Web of Knowledge by year and by subfield of Raman spectroscopy. Additional information is gleaned from presentations featuring Raman spectroscopy presented at the XXIII International Conference on Raman Spectroscopy in Bangalore, India, in August 2012 and at Scientific Exchange 2012 sponsored by the Federation of Analytical Chemistry and Spectroscopy Societies in Kansas City, Missouri, USA, October 2012. Papers published in the Journal of Raman Spectroscopy in 2011 are highlighted in this review and reflect trends at the cutting edge of Raman spectroscopy, a field that is expanding rapidly as a sensitive photonic probe of matter at the molecular level with an ever widening sphere of novel applications. Copyright © 2012 John Wiley & Sons, Ltd.     

Raman spectroscopy: Probing dynamics of water molecules confined in nanoporous silica glasses

In order to explore the influence of nanoscopic confinement on the vibrational properties of H-bonded liquids, we performed a detailed Raman scattering study, as a function of temperature, on water confined in 75 ? and 200 ? pores of a Gelsil glass. A detailed evaluation of the observed changes in the O-H stretching profile has been achieved by decomposing the O-H band into individual components, corresponding to those found for bulk water and associated to different levels of water connectivity. As main result, a similar effect produced by enlarging pore diameter and lowering T has been put into evidence. Again, the “structure-breaker” role of the GelSil glass on physisorbed water is confirmed and shown to be enhanced by the diminishing of the pore size.     

Raman spectroscopy study of lattice dynamics of macro-, micro-, and nanostructured barium titanates

The temperature dependences of the components A ₁(2TO) and E(1TO) of the soft ferroelectric mode during phase transitions in single crystals, ceramics, polycrystalline and epitaxial thin films of barium titanate, as well as a superlattice consisting of alternating layers of barium and strontium titanates, have been studied using the Raman spectroscopy method. Abrupt changes in soft mode frequencies have been observed in the single crystal during phase transitions between tetragonal, orthorhombic, and rhombohedral phases. Smoothing of the temperature dependences of soft modes and the coexistence of phases have been observed in ceramics and polycrystalline films. In the epitaxial film, the sequence of structural transformations fundamentally differs from that observed in the single crystal; in the superlattice, the ferroelectric phase is stable to 550 K.     

Sub-picosecond Raman spectroscopy and dynamics of nonequilibrium electrons and phonons in semiconductors

Recent progress made in the use of time-resolved pump-probe Raman scattering technique to study the dynamics of photo-excited nonequilibrium carriers and LO-phonons in III–V semiconductors up to the sub-picosecond time scale will be discussed. It will be shown how this technique has allowed direct time-domain measurements of electron-LO-phonon scattering times for “hot” carriers and lifetimes for “hot” LO-phonons in semiconductors like GaAs. The presentation will include new experimental results of Kash, Jha and Tsang on picosecond Raman studies of the Fröhlich interaction in alloys like Al _x Ga _1?x As and In _x Ga _1?x As. The present theoretical understanding of the dynamics of the highly excited carriers, dominated by strong LO-phonon emission, will be examined along with the discussion of a recent calculation of transient electrical conductivity of such hot carriers, showing extremely interesting oscillations with respect to the pump laser frequency, on the scale of the long wavelength LO-phonon frequency, and a highly nonlinear behaviour as a function of time.     

Theoretical investigation on Raman induced kerr effect spectroscopy in nonlinear confocal microscopy

The imaging theory of Raman induced Kerr effect spectroscopy (RIKES) in nonlinear confocal microscopy is presented in this paper. Three-dimensional point spread function (3D-PSF) of RIKES nonlinear confocal microscopy in isotropic media is derived with Fourier imaging theory and RIKES theory. The impact of nonlinear property of RIKES on the spatial resolution and imaging properties of confocal microscopy have been analyzed in detail. It is proved that RIKES nonlinear confocal microscopy can simultaneously provide more information than two-photon confocal microscopy concerning molecular vibration mode, vibration orientation and optically induced molecular reorientation, etc. It is shown that RIKES nonlinear confocal microscopy significantly enhances the spatial resolution and imaging quality of confocal microscopy and achieves much higher resolution than that of two-photon confocal microscopy.