Gas Phase Spectroscopic Studies of Hydroquinone Dimer

Abstract

Hydroquinone is one of the molecules that forms organic inclusion compounds, which have a wide range of commercial and technological applications. A lot of work has been done on this important molecule in the solid phase, but so far no work has been reported on its homoclusters in the gas phase. We report here the spectroscopic study of the hydroquinone dimer carried out under the jet-cooled conditions using the resonantly enhanced multiphoton ionization (REMPI) technique. The REMPI spectrum was quite rich in terms of the low-frequency transitions indicative of substantial geometry change upon excitation. The number of possible conformers formed in the jet was identified using the hole-burning spectroscopy. Ab initio calculations at the Hartree−Fock, density functional theory level using B3LYP functional and MP2 level for the ground state and the CIS level for the first excited state were carried out to understand the Franck−Condon activity in the spectrum as well as the number of possible stable conformers.