Vibrational Modes of the Vinyl and Deuterated Vinyl Radicals

Abstract

Following the initial report of the detection of fundamental transitions of all nine vibrational modes of the vinyl radical [Letendre , L. ; Liu , D.-K. ; Pibel , C. D. ; Halpern , J. B. ; Dai , H.-L. J. Chem. Phys. 2000 , 112 , 9209] by time-resolved IR emission spectroscopy, we have re-examined the assignments of the vibrational modes through isotope substitution. Precursor molecules vinyl chloride-d3, vinyl bromide-d3, and 1,3-butadiene-d6 are used for generating vibrationally excited vinyl-d3 through 193 nm photolysis. The nondeuterated versions of these molecules along with vinyl iodide and methyl vinyl ketone are used as precursors for the production of vinyl-h3. IR emission following the 193 nm photolysis laser pulse is recorded with nanosecond time and approximately 8 cm(-1) frequency resolution. A room-temperature acetylene gas cell is used as a filter to remove the fundamental transitions of acetylene, a photolysis product, in order to reduce the complexity of the emission spectra. Two-dimensional cross-spectra correlation analysis is used to identify the emission bands from the same emitting species and improve the S/N of the emission spectra. Isotope substitution allows the identification of several low-frequency vibrational modes. For C2H3, the assigned modes are the nu4 (CC stretch) at 1595, nu5 (CH2 symmetric bend) at 1401, nu6 (CH2 asymmetric + alpha-CH bend) at 1074, nu8 (CH2 + alpha-CH symmetric out-of-plane (oop) bend) at 944, and nu9 (CH2 + alpha-CH asymmetric oop bend) at 897 cm(-1). For C2D3, the modes are the nu5 (CD2 symmetric bend) at 1060, nu6 (CD2 asymmetric + alpha-CD bend) at 820, and nu8 (CD2 + alpha-CD symmetric oop bend) at 728 cm(-1).

Spectroscopic characterization of the complex of vinyl radical and carbon dioxide: Matrix isolation and ab initio study

“…During the past decades, this species has been extensively characterized by various spectroscopic techniques, both in the gas and solid phases. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The experimental studies have provided basic knowledge of the structure and vibrational spectra of vinyl radicals, which is in agreement with the state-of-the-art calculations. [15][16][17] Noncovalent interactions play an important role in many chemical, physical, and biological processes.…”

Accurate structure, thermodynamics, and spectroscopy of medium-sized radicals by hybrid coupled cluster/density functional theory approaches: The case of phenyl radical

“…Concerning particularly difficult analyzes of experimental spectra of free radicals, it has already been shown (e.g., for the F 2 NO 20 or vinyl 18,121,122 radicals) that accurate computational studies can lead to correction of the vibrational frequencies assignment. Actually, for the vinyl radical the discrepancies observed between the computed and experimental gas-phase infrared spectrum 123 led to an experimental re-investigation, 124 which in turn confirmed the theoretical predictions. In this frame, it is suggested that the 1400-1600 cm −1 spectral zone of C 6 H 5 , where bands due to precursor and water impurities are clearly present as well as the assignment of υ 23 of C 6 D 5 should be re-investigated with the help of fully anharmonic IR and/or Raman simulated spectra, also accounting for the species possibly present in the experimental mixture and, in case, including a few sets of isotopically substituted precursors.…”

Large cross section for super energy transfer from hyperthermal atoms to ambient molecules

“…The details of our time-resolved Fourier transform infrared (TR-FTIR) emission spectroscopy experiment have been described previously [31,32], and are reviewed in the Supplemental Material. Briefly, a mixture of SO 2 , hydrogen bromide (HBr), and argon (Ar) gas is continuously flowed through a reaction cell, and irradiated with 193 nm pulses from an ArF excimer laser.…”