Laser‐induced anisotropy and depolarization ratios

Monobeam transmission and resonance Raman (RR) experiments were used to study the excited state S m ← S 3 (B) spectra and the depolarization ratios, ρ n , of the ν 2 (Cβ–Cβ), A 1 g , \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop \nu \limits^ - = 1558{\rm cm}^{ - {\rm 1}} $\end{document} , and δ(pyr), A 1 g , \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop \nu \limits^ - = 1643{\rm cm}^{ - {\rm 1}} $\end{document} RR peaks of meso ‐tetrakis( N ‐methyl‐4‐pyridyl)porphine, H 2 TMpyP(4), in phosphate buffer (pH 7) at an excitation of λ 1 = 422 nm ( \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop {\nu _1 }\limits^ - = 23697{\rm cm}^{ - {\rm 1}} $\end{document} ) as a function of pump intensity, I 1 (mW), over the range of I 1 = 0–5 mW. Three factors, ground state depletion, induced anisotropic density distribution of the ground stage, n 1 G , and the anisotropic polarized excited‐state absorption effect, are discussed to explain the behaviour of ρ n versus I 1 for these two peaks. In addition, scattering tensors and experimentally determined depolarization ratios for the \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop \nu \limits^ - = 1558{\rm cm}^{ - {\rm 1}} $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop \nu \limits^ - = 1643{\rm cm}^{ - {\rm 1}} $\end{document} RR peaks of H 2 TMpyP(4) at excitations of λ 1 = 422, 476.5 and 514.5 nm ( \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta \mathop \nu \limits^ - = 23697,{\rm 20986 and 19436 cm}^{ - {\rm 1}} $\end{document} , respectively) are presented. The results seem to imply that a > b , and could be interpreted as the presence of x ‐ and y ‐splitting of the Soret B band.