Polycyclic aromatic hydrocarbons (PAHs) and their substituted derivatives are found in great variety in ature. They form a series of compounds with graded chemical and physical properties which have made them favourite subjects for quntitative evaluation of the relation between the structure and chemical reactivity or other haracteristics. These molecules have been studied for last several years by using coonventional and non-conventional techniques. Photoacoustc (PA) spectroscopy has emerged as a versatile technique to characterize materials in any form with unique capability and sensitivity. This technique not only reveals non-radiative transitions between excited to excited states but also provides information about forbidden singlet-triplet transitions which are not observed normally by the conventional spectroscopy. SThe present paper deals with the PA studies of 1,3-dihydroxy naphthalene (1,3-DHN) molecule. SThe study of electronic transitions of 1,3-DHN is reported using PA and optical spectra in boric acid glass in the region 250-400 nm. The electronic transitions of the molecule observed experimentally, have been interpreted using the optimized geometries and CNDO/S-CI method. A good agreement is found between the experimental and calculated results. Assignments of the observed electronic transitioons are made on the basis of singlet-singlet and singlet-triplet transitions. Vibrations attached to these electronic transitions are attributed to the ground state vibrational modes of naphthalene molecule.
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