A STUDY OF THE EXCITED-STATE STRUCTURE AND VIBRATIONS OF HYDROQUINONEBY AB-INITIO CALCULATIONS AND RESONANT 2-PHOTON IONIZATION SPECTROSCOPY

Hydroquinone (HYQ) in the lowest electronically excited state has been studied by ab initio quantum chemical calculations and resonant two-p hoton ionization (R2PI) spectroscopy. Calculations ar. the MP2/6-31G and CIS/6-31G levels yield satisfactory results on structures and vib rational frequencies of the cis-HYQ and trans-HYQ in both the S-0 and S-1 states. Only transitions involving in-plane modes are observed in the R2PI spectrum of HYQ. All spectral bands including some newly obse rved ones have been successfully assigned with the help of our compute d results and analogy with the reported spectra for similar molecules. (C) 1997 Elsevier Science B.V.