The S-0 -> S-1 cavity ring-down absorption spectrum of jet-cooled azulene:dependence of internal conversion on the excess energy

The S-0--> S-1 cavity ring-down (CRD) absorption spectrum of jet-cooled azu lene 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 v ibronic states up to excess energies of similar to hcx2500 cm(-1). A value for the S-1,S-0 lifetime of approximate to 2.6 +/- 0.4 ps was found. New ex perimental evidence for a conical intersection of the S-0 and S-1 potential s at approximate to 2100 +/- 100 cm(-1) was found. The possibility of azule ne being one of the carriers of the diffuse interstellar bands (DIB) is bri efly discussed.