Investigation of broad molecular absorption bands with the help of line shape analysis in coherent Raman scattering experiments

Abstract

The line shape observed in coherent Raman scattering (CRS) with excitation under conditions of electronic resonance is discussed, For the case of A-type scattering, the complex Raman amplitude is related directly to the molecular one-photon absorbance of the resonance transition concerned. The basis for this relation is transform theory, a method known from spontaneous resonance Raman scattering to relate the Raman excitation profile to the observed molecular absorbance. Features of the Raman amplitude, determining the observed line shapes for coherent anti-Stokes Raman scattering (CARS) and for coherent Stokes Raman scattering (CSRS), are discussed qualitatively. The discussion considers two typical forms in which broad molecular absorption spectra of polyatomic molecules in the condensed phases appear. Inhomogeneous broadening leads to characteristic changes of the Raman amplitude in relation to molecular absorbance in the case of CSRS (for molecules in the electronic ground state), whereas for CARS the relation derived in the homogeneous broadened case remains valid. The special advantages of the CRS technique for determining the complex non-Raman resonant (background) susceptibiiity from concentration dependence are demonstrated. I A ( w ) =-rr Im ao(w)is related to the Raman excitation profile t

Experimental and theoretical investigation of tunable picosecond pulse generation in longitudinally pumped dye laser generators and amplifiers

“…The solvents methanol [72], ethylene glycol [73] and DMSO [74] have no vibrational transitions at the measured frequency shifts. The Raman transitions are resonantly enhanced by the S 0 -S l absorption of the pump laser [43][44][45][46][47].…”

Spontaneous and Coherent Resonance Raman Scattering by Multimode Systems; Transform Laws for Excitation Profiles

“…The distribution of purely electronic transition energies is considered to be Lorentzian35, 36,50,51 or Gaussian.19,37,52 In the Lorentzian case, it was shown that for CARS, as for absorption, the linewidth is a sum of homogeneous and inhomogeneous broadening35,36 and, therefore, the transform law remains correct for CARS (but it does not hold for REP or CSRS excitation proÐles). In the case of a broad Gaussian inhomogeneous distribution, which, in the authorsÏ opinion,37 is a more realistic representation of the e †ect of environment/solution, the transform laws will not work either for REPs and CSRS or for CARS.…”

Transform relations for CARS excitation profiles

“…In the case of coherent anti-Stokes Raman scattering, the excitation profile of CARS can be determined via the amplitude of spontaneous Raman scattering as follows [6][7][8][9]:…”

“…Later these techniques have been extended to the analysis of the experimental data from resonance CARS (coherent anti-Stokes Raman scattering) -CEPs [6][7][8][9].…”