Cavity ring-down UV spectroscopy of the C2Σ+-X2Π electronic transition of CH

Abstract

Rotationally resolved spectra of the C 2 Σ + -X 2 Π electronic system of the CH radical were measured using cavity ring-down spectroscopy in supersonically expanding, planar hydrocarbon plasma. The experimental conditions allowed the study of highly excited rotational levels starting from vibrationally excited states. Here we present some 200+ new or more accurately recorded transitions in the 0-0, 1-1 and 2-2 vibronic bands in the ultraviolet between 30900-32400 cm -1 (324-309 nm). The resulting data, compared to earlier measurements, allows for the determination of more precise molecular constants for each vibrational state and therefore more precise equilibrium values. From this an equilibrium bond length of 1.115798(17) Å for the C 2 Σ + state is determined. A comprehensive list with observed transitions for each band has been compiled from all available experimental studies and constraints are placed on the predissociation lifetimes.

Analysis of measured high-resolution doublet rovibronic spectra and related line lists of 12CH and 16OH

“…The full list of data sources employed in the final MARVEL analysis 9,10,20,62,63,66,73,74,[76][77][78][79]81,83,84,87,[89][90][91][92][93][94][95][96][97]99,101,102,105 of 12 CH is given in Table 1, which also provides details of the range of wavenumbers and the number of transitions measured and validated for each vibronic band, with some statistical analysis of the uncertainties characterizing the source segments. After careful analysis, altogether 29 sources could be utilized, covering a total of 6348 transitions.…”

“…1 for the states covered in this study). To do this we analyze the experimental spectroscopic data available for the parent 12 CH 6,9–15,20,40,51,62–105 and 16 OH 8,21,31,38,41,43–47,52,53,106–158 isotopologues, using the Hamiltonian-free M arvel procedure, 1–5 and obtain high-accuracy empirical rovibronic energy levels with well-defined uncertainties. The empirical energy levels obtained allow the critical assessment of line lists 9,51–53 created previously for the two radicals.…”