The S0→S1 cavity ring-down absorption spectrum of jet-cooled azulene: dependence of internal conversion on the excess energy

Abstract

The S₀→S₁ cavity ring-down (CRD) absorption spectrum of jet-cooled azulene is reported in the spectral region between 14275 and 17300 cm^-1. The excess energy dependence of the fast internal conversion rate k_ic (S₁S₀) was investigated in the frequency domain by evaluating the linewidths of vibronic states up to excess energies of ∽hc×2500 cm^-1. A value for the S_1,0 lifetime of ≈2.6±0.4 ps was found. New experimental evidence for a conical intersection of the S₀ and S₁ potentials at ≈2100±100 cm^-1 was found. The possibility of azulene being one of the carriers of the diffuse interstellar bands (DIB) is briefly discussed.