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Title: Frequency-comb referenced spectroscopy of v₄₋ and v₅₋excited hot bands in the 1.5 and μm spectrum of C₂H₂

Doppler-free transition frequencies for v₄₋ and v₅₋excited hot bands have been measured in the v₁ + v₃ band region of the spectrum of acetylene using saturation dip spectroscopy with an extended cavity diode laser referenced to a frequency comb. The frequency accuracy of the measured transitions, as judged from line shape model fits and comparison to known frequencies in the v₁ + v₃ band itself, is between 3 and 22 kHz. This is some three orders of magnitude improvement on the accuracy and precision of previous line position estimates that were derived from the analysis of high-resolution Fourier transform infrared absorption spectra. Comparison to transition frequencies computed from constants derived from published Fourier transform infrared spectra shows that some upper rotational energy levels suffer specific perturbations causing energy level shifts of up to several hundred MHz. These perturbations are due to energy levels of the same rotational quantum number derived from nearby vibrational levels that become degenerate at specific energies. Future identification of the perturbing levels will provide accurate relative energies of excited vibrational levels of acetylene in the 7100–7600 cm⁻¹ energy region.
 [1] ;  [2] ;  [3] ;  [1] ;  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Stony Brook Univ., Stony Brook, NY (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States); Stony Brook Univ., Stony Brook, NY (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 0022-2852; R&D Project: CO006; KC0301020; TRN: US1500645
Grant/Contract Number:
SC00012704; AC02-98CH10886
Accepted Manuscript
Journal Name:
Journal of Molecular Spectroscopy
Additional Journal Information:
Journal Volume: 361; Journal ID: ISSN 0022-2852
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY acetylene; vibrational spectroscopy; energy levels; frequency comb; perturbations; sub-Doppler spectroscopy; Lamb dip