Ground and first electronic excited state vibrational modes of the methyl-p-aminobenzoate molecule

Laser induced fluorescence, dispersed emission and two-colour ionisation sp ectroscopy (including the ionisation energy threshold) are suggested as an appropriate set of experimental methods for drawing the ground and excited state vibrational spectra of large organic molecules in presence of solvate d molecules and dimers. In this Letter, they have been applied to obtain th e vibrational spectrum of methyl-p-aminobenzoate (MAB). Parallel ground sta te ab initio calculations have enabled the geometry to be determined and th e vibrational modes to be accurately assigned. The comparison of the ground and the first electronic excited state vibrational band wavenumbers shows an excellent agreement except for the excited state bands observed at 52.2, 565.6 and 579.7 cm(-1). (C) 1999 Elsevier Science B.V. All rights reserved .