Cavity ring-down UV spectroscopy of the C 2 Σ + -X 2 Π electronic transition of CH

Chris Medcraft*, Harold Linnartz, Wim Ubachs

*Corresponding author for this work

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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 and 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.

Original languageEnglish
Pages (from-to)15-23
Number of pages9
JournalJournal of Molecular Spectroscopy
Early online date19 Apr 2019
Publication statusPublished - Jun 2019


The authors thank Carla Kreis and Xavier Bacalla for assistance during part of the measurements. This work has been supported through a grant within the framework of the Dutch Astrochemistry Network funded by NWO (Netherlands Organisation for Scientific Research). Appendix A See . Tables 3–5 Appendix B

FundersFunder number
Horizon 2020 Framework Programme670168
Nederlandse Organisatie voor Wetenschappelijk Onderzoek


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