Knowledge Bank

Two-photon electronic absorption spectra of the tropyl radical (cyclic $C7H7$) have been observed by Resonance Enhanced Multiphoton Ionization Spectroscopy (REMPI) from 415 to 590 nm, corresponding to 34000 to 48000 $cm-1$. Two Rydberg series are assigned and an ionization potential determined: $n$p, $\delta =0.35$; $n$f, $\delta =0.05$; $IP=50177$ $cm-1$. Vibrational activity of the Rydberg states was observed and the frequencies were found to be similar to the ion: $\omega 2=862cm-1$ (ring breathing), $2\omega 18=1528cm-1$ (ring bending), and $2\omega 20=1284cm-1$ (CH out-of-plane bend).