Femtosecond stimulated Raman scattering for polyatomics with harmonic potentials: application to rhodamine 6G.
The perturbation theory of stimulated Raman scattering (SRS), with Raman pump on minus pump off and heterodyne detection along the probe direction, is reviewed. It has four third-order polarization terms, labeled as SRS or inverse Raman scattering (IRS): SRS(I), SRS(II), IRS(I), and IRS(II). These four polarizations have a wave packet interpretation. The polarizations, with homogenous and inhomogeneous broadening included, can be written as integrals over four-time correlation functions, and analytic formulas are derived for the latter for multidimensional harmonic potential surfaces with Franck-Condon displacements in the modes which facilitates the calculation of the SRS cross sections. The theory is applied to understand recent experimental results on the femtosecond SRS (FSRS) of a fluorescent dye, rhodamine 6G (R6G), where the Raman pump pulse is about 1 ps long, and the probe pulse is about 10 fs. The calculations compared very well with the R6G experimental results for off-resonance and resonance FSRS spectra spanning both Stokes and anti-Stokes bands, and for negative and positive pump-probe delay times on resonance.
Niu
Kai
K
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore.
Cong
Shulin
S
Lee
Soo-Y
SY
D000042:Absorption; D005456:Fluorescent Dyes / Q000737:chemistry*; D005583:Fourier Analysis; D012235:Rhodamines / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013997:Time Factors
D005456:Fluorescent Dyes; D012235:Rhodamines; C026188:rhodamine 6G