Cavity ring-down laser absorption spectroscopy of jet-cooled anthracene

Polycyclic aromatic hydrocarbons (PAHs) have been suggested as possible carriers of diffuse interstellar bands. To verify this, absorption spectra of PAHs under conditions similar to those encountered in the interstellar medium should be obtained. We report here the application of cavity ring-down laser absorption spectroscopy to the study of neutral anthracene expanded in supersonic jets. Absorption spectra of the S-1<--S-0 transition of anthracene near 361 nm have been obtained with significantly higher resolution than reported previously. Assignments of the vibrational modes involved in the sequence bands observed on the red side of the origin band are proposed.