title: Excited electronic state mixing in 7-azaindole. Quantitative measurements using the Stark effect.
abstract: Stark effect measurements of the +280 cm(-1) vibronic band at ∼286 nm in the high resolution S1-S0 fluorescence excitation spectrum of 7-azaindole (7AI) in a molecular beam show that the permanent (electric) dipole moment (PDM) of the upper state vibrational level reached in this transition is 4.6 D, twice as large as the PDM of the zero-point level of the S1 state. This large difference is attributed to state mixing with a more polar state. EOM-CSSD calculations suggest that this more polar state is σπ* in nature and that it crosses the ππ* state in energy along the coordinate connecting the two potential energy minima. Such state mixing apparently provides more facile access to conical intersections with the ground state, and subsequent hydrogen atom detachment reactions, since independent studies by Sakota and Sekiya have shown that the N-H stretching frequency of 7AI is significantly reduced when it is excited to the +280 cm(-1) vibrational level of the S1 state.
authors.affiliation: Department of Chemistry, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Justin W
authors.initials: JW
authors.lastname: Young
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Pozun
authors.forename: Kenneth D
authors.initials: KD
authors.lastname: Jordan
authors.forename: David W
authors.initials: DW
authors.lastname: Pratt
mesh_terms: D004583:Electrons; D006859:Hydrogen / Q000737:chemistry; D007211:Indoles / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D013816:Thermodynamics; D014466:Ultraviolet Rays; D014732:Vibration
chemical_list: C023422:7-azaindole dimer; D007211:Indoles; D006859:Hydrogen