The rotationally resolved two-photon excitation spectrum of the Q-branch (¿J = 0) of the O00 band in the S1 ¿ S0 transition of DABCO was recorded in a cell at room temperature. Two counterpropagating narrow bandwidth laser beams were used for Doppler-free excitation. The observed linewidth was 20 MHz. Analysis of the spectra provides the change upon electronic excitation of the rotational constants.
- vanderwaals complexes