Low temperature laser fluorescence and excitation spectra of free base phthalocyanine in normal alkanes matrices (Shpolskii effect)

Excitation and fluorescence spectra of free base phthalocyanine were studied in matrices of normal alkanes (C₈H₁₈, C₁₂H₂₆, C₁₆H₃₄) at low temperatures (5 to 30 K). Narrow band excitation of fluorescence using a pulsed tunable dye laser was used for site selection to eliminate ambiguities due to impurities and multiple sites. Fluorescence and excitation spectra show quasiline structure. Multiplicity of 0-0 transitions depends on the chain length of normal alkanes. The spectra and frequencies of normal vibrations are compared with those of phthalocyanine in other n-alkanes (C₉H₂₀, C₁₀H₂₂) and noble gas matrices (Ar, Ne) under different excitation conditions.