Resonance Raman and Optical Dephasing Study of Tricarbocyanine Dyes
Stephen H. Ashworth,
Andreas Kummrow
and Kurt Lenz
Fluorescence line shape analysis based on resonance Raman spectra of
HITCI is used to determine the details and magnitude of the
vibrational part of the line broadening function.
Forced Light Scattering (FLS) is applied to measure optical dephasing
of HITCI in ethylene glycol, pumping at 770 nm with 20 fs pulses from
a Ti:sapphire laser and probing with continuous wave light from an
argon ion laser. The observed response is well described by the line
broadening function derived from the fluorescence line shape.
High frequency vibrational modes not covered directly by the laser
spectrum account for 20 % of the vibration induced broadening in the
FLS experiment. This effect is explained by difference frequency
mixing with thermally populated low frequency vibrations.