Collisional energy transfer of vibrationally highly excited molecules. V. UV absorption study of azulene
Vibrationally highly excited azulene molecules in the electronic ground state (excitation energy <E>=30 600 cm-1) were produced by excitation with a N2 laser. The stepwise deactivation of the excited molecules in collisions with a variety of 23 inert bath gases was monitored by time-resolved hot UV absorption spectroscopy at 290 nm. Using previously determined calibration curves of the absorption coefficient at 290 nm as a function of the excitation energy <E>, energy-loss curves <E(t)> were recorded and analyzed with respect to the average energies <∆E> transferred per collision. The dependencies of <∆E> on the excitation energy <E> were derived. In most cases, <∆E> was found to be only weakly dependent on <E> above 10 000 cm-1, whereas a stronger rise with energy became apparent only at lower energies. A comparison with earlier IR emission experiments on the azulene system is given.