Vibrational bands of luminescent zinc(II)-octaethyl-porphyrin using a polarization-sensitive 'microcopic' multiplex CARS technique

Polarization-sensitive, multiplex coherent anti-Stokes Raman scattering (ps-MCARS) has been used to detect the vibrational bands of the highly luminescent zinc(II)-octaethylporphyrin (Zn-OEP). We show here that ps-MCARS can be used to measure the vibrational bands under resonant conditions. Polarization-sensitive CARS further helps to resolve composite and overlapping Raman bands on the basis of variations in vibrational symmetry. This paper also exemplifies the advantages of multiplex CARS (MCARS) spectroscopy carried out under tight focusing conditions as proposed earlier. We demonstrate that a microscopic CARS focusing and collection system in combination with the multiplex technique allows a reduction in the amount of sample and a shortening of the measurement time. We analyse the relationship between the coherent vibrational phases and the symmetry of the different vibrational band of Zn-OEP skeletal modes. The values of the coherent vibrational phases are similar for vibrational bands with the same symmetry.