title: Mid-IR spectra of different conformers of phenylalanine in the gas phase.
abstract: The experimental mid- and far-IR spectra of six conformers of phenylalanine in the gas phase are presented. The experimental spectra are compared to spectra calculated at the B3LYP and at the MP2 level. The differences between B3LYP and MP2 IR spectra are found to be small. The agreement between experiment and theory is generally found to be very good, however strong discrepancies exist when -NH2 out-of-plane vibrations are involved. The relative energies of the minima as well as of some transition states connecting the minima are explored at the CCSD(T) level. Most transition states are found to be less than 2000 cm(-1) above the lowest energy structure. A simple model to describe the observed conformer abundances based on quasi-equilibria near the barriers is presented and it appears to describe the experimental observation reasonably well. In addition, the vibrations of one of the conformers are investigated using the correlation-corrected vibrational self-consistent field method.
authors.affiliation: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany. helden@fhi-berlin.mpg.de
authors.forename: G
authors.initials: G
authors.lastname: von Helden
authors.forename: I
authors.initials: I
authors.lastname: Compagnon
authors.forename: M N
authors.initials: MN
authors.lastname: Blom
authors.forename: M
authors.initials: M
authors.lastname: Frankowski
authors.forename: U
authors.initials: U
authors.lastname: Erlekam
authors.forename: J
authors.initials: J
authors.lastname: Oomens
authors.forename: B
authors.initials: B
authors.lastname: Brauer
authors.forename: R B
authors.initials: RB
authors.lastname: Gerber
authors.forename: G
authors.initials: G
authors.lastname: Meijer
mesh_terms: D005740:Gases / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D010649:Phenylalanine / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000295:instrumentation / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000295:instrumentation / Q000379:methods; D014732:Vibration
chemical_list: D005740:Gases; D010649:Phenylalanine