Nonlocal hyper-Rayleigh scattering from liquid nitrobenzene.

Area of Science:

• Nonlinear Optics
• Molecular Spectroscopy
• Condensed Matter Physics

Background:

• Hyper-Rayleigh scattering (HRS) probes molecular hyperpolarizability.
• Understanding collective effects in polar liquids is crucial for nonlinear optics.
• Previous models often treated molecular contributions separately.

Purpose of the Study:

• To investigate the contributions of different molecular hyperpolarizability components to HRS in a polar liquid.
• To analyze the role of collective molecular dynamics in scattering intensity.
• To validate theoretical models of coherent and incoherent scattering processes.

Main Methods:

• Experimental measurement of Hyper-Rayleigh scattering (HRS) intensity.
• Varying incident and scattered light polarization states.
• Measurements conducted at various scattering angles near 90 degrees for liquid nitrobenzene.

Main Results:

• HRS intensity is significantly influenced by the polar transverse collective mode.
• Evidence supports long-range dipole-dipole orientation correlations.
• Coherent HRS originates from the vector part (beta((1))) of the first hyperpolarizability.
• HRS from the octupolar part (beta((3))) is local and incoherent.

Conclusions:

• Collective molecular modes play a dominant role in HRS from polar liquids.
• The study confirms the model of coherent scattering arising from intermolecular correlations.
• Distinguishes between coherent scattering contributions (beta((1))) and incoherent contributions (beta((3))).