Atlas of new and revised high-resolution spectroscopy of six CO isotopologues in the 101–115 nm range

Transition energies of the v′ = 0, 1, 2, and 3 to v′′ = 0 bands of the B¹Σ⁺, C¹Σ⁺, and E¹Π to X¹Σ⁺ states, related term values, and molecular constants

¹ Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS – Université Paris-Sud (UMR 8214), 91405 Orsay, France
e-mail: jean-louis.lemaire@u-psud.fr
² Observatoire de Paris, LERMA, UMR 8112 du CNRS, Meudon, France
³ Université Versailles St-Quentin, Sorbonne Universités, UPMC Paris 06, CNRS/INSU, LATMOS-IPSL, 78280 Guyancourt, France
⁴ Department of Physics, Wellesley College, Wellesley, MA 02481, USA
⁵ Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606, USA
⁶ School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85281, USA
⁷ DESIRS Beam Line, Synchrotron SOLEIL, Saint Aubin, France

Received: 17 October 2017
Accepted: 15 November 2017

Abstract

Our knowledge of astronomical environments containing CO depends on accurate molecular data to reproduce and interpret observed spectra. The recent and future improvements of ultraviolet space instrumentation, both in sensitivity and resolution, require increasingly detailed laboratory molecular spectroscopy as a reference. As part of a long-term experimental campaign at the SOLEIL Synchrotron facility, we have acquired gas-phase absorption spectra of six CO isotopologues in the vacuum ultraviolet. These spectra are recorded using the Fourier-transform spectrometer installed on the DESIRS beamline, providing a unique resolving power up to 10⁶ in the 8–13 eV range. We have used resolutions in the 300 000–450 000 range for this campaign, which enable the analysis of individual line positions. We report new measurements on neighboring Rydberg states in the 101–115 nm range that could also be used as f-value calibrators, namely B¹Σ⁺, C¹Σ⁺, and E¹Π, for six CO isotopologues. This range encompasses the absorption transitions B(v′ = 0, 1, and 2), C(v′ = 0, 1, 2, and 3), and E(v′ = 0, 1, 2, and 3) from X¹Σ⁺(v′′ = 0). Higher resolution laser-based measurements of CO isotopologues from the literature are used to improve the absolute calibration and accuracy of our data. The overall uncertainty of the great majority of the line positions presented in this atlas is estimated to be 0.01 cm⁻¹. In addition, some of the data derived from transition energies measurements, such as term values and molecular constants, are obtained for the first time, and others are improvements on previous sparser or lower spectral resolution datasets.