The R2PI spectroscopy of tyrosine: A vibronic analysis

Based on an infrared spectrum in an atlas, and on a Raman spectrum that we acquired ourselves, we have made a frequency assignment for the vibrational modes of tyrosine. This assignment was aided by the results of a GAUSSIAN frequency calculation that we performed at the Hartree-Fock level, using the 3-21G basis set. We have made a vibronic assignment of the bands in a jet-cooled LD-R2PI spectrum that we obtained for tyrosine, using the aforementioned ground-state analysis as a guide. By UV hole burning, we have verified which of the low-frequency R2PI peaks are origins, assigning the others as torsions. We have assigned the various origin bands, with their associated bands to higher energy, to configurations in which the amino acid backbone is either gauche or anti to the ring. (C) 2002 Elsevier Science (USA).