Title: High resolution spectroscopy of jet cooled phenyl radical: The ν₁ and ν₂ a₁ symmetry C–H stretching modes

Abstract

A series of CH stretch modes in phenyl radical (C₆H₅) has been investigated via high resolution infrared spectroscopy at sub-Doppler resolution (~60 MHz) in a supersonic discharge slit jet expansion. Two fundamental vibrations of a1 symmetry, ν₁ and ν₂, are observed and rotationally analyzed for the first time, corresponding to in-phase and out-of-phase symmetric CH stretch excitation at the ortho/meta/para and ortho/para C atoms with respect to the radical center. The ν₁ and ν₂ band origins are determined to be 3073.968 50(8) cm^–1 and 3062.264 80(7) cm^–1, respectively, which both agree within 5 cm^–1 with theoretical anharmonic scaling predictions based on density functional B3LYP/6-311g++(3df,3dp) calculations. Integrated band strengths for each of the CH stretch bands are analyzed, with the relative intensities agreeing remarkably well with theoretical predictions. Frequency comparison with previous low resolution Ar-matrix spectroscopy reveals a nearly uniform Δν ≈ + 10-12 cm^–1 blue shift between gas phase and Ar matrix values for ν₁ and ν₂. This differs substantially from the much smaller red shift (Δν ≈ – 1 cm^–1) reported for the ν₁₉ mode, and suggests a simple physical model in terms of vibrational mode symmetry and crowding due to the matrix environment. Lastly, the infrared phenyl spectramore » are well described by a simple asymmetric rigid rotor Hamiltonian and show no evidence for spectral congestion due to intramolecular vibrational coupling, which bodes well for high resolution studies of other ring radicals and polycyclic aromatic hydrocarbons. In summary, the combination of slit jet discharge methods with high resolution infrared lasers enables spectroscopic investigation of even highly reactive combustion and interstellar radical intermediates under gas phase, jet-cooled (T_rot ≈ 11 K) conditions.« less

Authors:

Chang, Chih-Hsuan ^[1]; Nesbitt, David J. ^[1]

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+ Show Author Affiliations

1. Univ. of Colorado, Boulder, CO (United States)

Publication Date:

Mon Jul 25 00:00:00 EDT 2016

Research Org.:

Univ. of Colorado, Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); National Science Foundation (NSF)

OSTI Identifier:

1924545

Alternate Identifier(s):

OSTI ID: 1272648

Grant/Contract Number:  

SC0002123; FG02-09ER16021; CHE 1266416; PHYS 1125844

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Chemical Physics

Additional Journal Information:

Journal Volume: 145; Journal Issue: 4; Journal ID: ISSN 0021-9606

Publisher:

American Institute of Physics (AIP)

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; High resolution spectroscopy; Density functional theory