title: State-by-state investigation of destructive interference in resonance Raman spectra of neutral tyrosine and the tyrosinate anion with the simplified sum-over-states approach.
abstract: UV resonance Raman scattering is uniquely sensitive to the molecular electronic structure as well as intermolecular interactions. To better understand the relationship between electronic structure and resonance Raman cross section, we carried out combined experimental and theoretical studies of neutral tyrosine and the tyrosinate anion. We studied the Raman cross sections of four vibrational modes as a function of excitation wavelength, and we analyzed them in terms of the contributions of the individual electronic states as well as of the Albrecht A and B terms. Our model, which is based on time-dependent density functional theory (TDDFT), reproduced the experimental resonance Raman spectra and Raman excitation profiles for both studied molecules with good agreement. We found that for the studied modes, the contributions of Albrecht's B terms in the Raman cross sections were important across the frequency range spanning the L(a,b) and B(a,b) electronic excitations in tyrosine and the tyrosinate anion. Furthermore, we demonstrated that interference with high-energy states had a significant impact and could not be neglected even when in resonance with a lower-energy state. The symmetry of the vibrational modes served as an indicator of the dominance of the A or B mechanisms. Excitation profiles calculated with a damping constant estimated from line widths of the electronic absorption bands had the best consistency with experimental results.
authors.affiliation: U.S. Army ECBC , RDCB-DRI-I/BLDG E5951, 5183 Blackhawk Road, Aberdeen Proving Ground, Aberdeen, Maryland 21010, United States.
authors.forename: Jerry B
authors.initials: JB
authors.lastname: Cabalo
authors.forename: Semion K
authors.initials: SK
authors.lastname: Saikin
authors.forename: Erik D
authors.initials: ED
authors.lastname: Emmons
authors.forename: Dmitrij
authors.initials: D
authors.lastname: Rappoport
authors.forename: Alán
authors.initials: A
authors.lastname: Aspuru-Guzik
mesh_terms: D000838:Anions / Q000737:chemistry*; D003198:Computer Simulation; D008958:Models, Molecular; D015394:Molecular Structure; D013059:Spectrum Analysis, Raman; D014443:Tyrosine / Q000737:chemistry*; D014732:Vibration
chemical_list: D000838:Anions; D014443:Tyrosine