Time-resolved anisotropic coherent anti-Stokes Raman scattering: A new probe of reorientational dynamics

Abstract

A formalism for the time-dependent anisotropic third-order susceptibility induced by a linearly polarized excitation pulse has been derived to describe the time dependence of coherent anti-Stokes Raman scattered (CARS) and Raman time-resolved experiments. The third-order susceptibility induced in a randomly oriented molecular system contains nine independent molecular parameters-three isotropic and six anisotropic--as compared to three independent parameters in an isotropic system. Methods of time-resolved anisotropic anti-Stokes Raman scattering (TRA CARS) are discussed as an approach to reorientational measurements. The dependence of the TRA CARS or TRA Raman signal on vibration and polarization component can in principle provide more rotational information than fluorescence depolarization or linear dichroism measurements and may allow more complete characterization of rotational dynamics. Results are reported for three types of TRA CARS experiments to demonstrate the capabilities of TRA CARS to study the rotational motion of molecules in liquids.

Orientational relaxation dynamics in aqueous ionic solution: Polarization-selective two-dimensional infrared study of angular jump-exchange dynamics in aqueous 6M NaClO4

“…[16][17][18] Theoretical models for rotational dynamics originating from librational, diffusive, and angular jump motions have been developed and applied to experimental studies of rotational dynamics in water and aqueous solutions. [19][20][21][22][23][24][25][26][27] For the diffusive motion of hydroxyl groups with an intact H-bond, models based on diffusive molecular rotors have been used. [28][29][30] These models result in single exponential relaxation of the hydroxyl group anisotropy with a time constant directly related to the orientational diffusion constant.…”

Polarization effects on intermolecular vibrational energy transfer analyzed by 2DIR spectroscopy

“…[4,8,9] Theoretical models for rotational dynamics originating from librational, diffusive and angular jump motions have been developed and applied to experimental studies of rotational dynamics in water and aqueous solutions. [10][11][12][13][14][15] Besides, polarization effects are useful for suppressing background signals [16,17] ] and even for enhancing cross peaks at the expense of diagonal peaks. [18] This is of particular interest because large diagonal peaks quite often mask weaker cross peaks and suppressing the diagonal peaks provides better resolution of the cross peaks.…”

Research of the Microscopic Polarizability Tensors for the Third and Fourth-Order Nonlinear Spectroscopy

“…Higher-order nonlinear spectroscopic techniques, such as the third order Coherent Anti-Stokes Raman Spectroscopy(CARS) and the fourth order Coherent Anti-Stokes Hyper-Raman Spectroscopy (CAHRS) have been recently employed to investigate or imaging molecular interfaces and biological membranes [1][2][3][4][5][6][7][8][9][10]. Being Raman spectroscopy, the clear advantage of the CARS and the CAHRS is that they do not directly use the infrared laser pulses that generally have trouble to penetrate the condensed phase as in the ordinary IR or SFG vibrational spectroscopy, for obtaining the coherent molecular vibrational spectra of the buried interfaces and membranes.…”