A pressure-induced phase transition is detected in crystals of anthraq
uinone at approximate to 2.3 GPa by Raman phonon spectra. Related fluo
rescence experiments indicate a phase transition mechanism similar to
that recently observed in 9,10-dihalogenated anthracene derivatives, l
eading to a less relaxed excimer state after the transition. Lattice d
ynamics calculations under pressure reproduce the observed phase trans
ition and confirm the transition mechanism.