Sub-Doppler High-Resolution Spectra of C6H6
We have measured the Doppler-free rotationally resolved two-photon spectrum of two vibronic bands of C6H6,\n14; 1; and 14; 1:. Compared to the 14; 1; band (E,,,, = 2492 cm-\u2019) a drastically reduced number of sharp\nlines is observed in the 14; 1: band (EexCe=88 3 412 cm-\u20191. The K = 0 rotational lines are still seen, while K #\n0 lines disappear. This can be understood in terms of Coriolis coupling between the 14l l2 state and other\nvibrational states within Sl and a subsequent nonradiative process. This coupling might be the explanation\nfor the drastic onset of line broadening in C6H6 at an excess energy of 3000 cm-l, \u201cchannel three\u201d. The line\nbroadening is then due to a different process than that responsible for the population lifetime of S1.