Atlas of new and revised high-resolution spectroscopy of six COisotopologues in the 101-115 nm range Transition energies of the u = 0, 1, 2, and 3 to u = 0 bands of the B 1 Σ + , C 1 Σ + , and E 1 Π to X 1 Σ + states, related term values, and molecular constants 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 10 6 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 B 1 Σ + , C 1 Σ + , and E 1 Π, 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 X 1 Σ + (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.Article published by EDP Sciences A114, page 1 of 62 A&A 614, A114 (2018) A114, page 3 of 62 A&A 614, A114 (2018)
Laser calibration benchmarks and associated dataAn absolute calibration of lines requires the availability of accurately determined standards, either atomic or molecular, as close as possible to the lines under study. There are many reported laser-based measurements of CO VUV transitions with accurate absolute calibrations based on primary standards. Some previous work has been limited to a few lines of each vibrational band, while others offer almost complete bands for use as comparisons for calibration purposes. Data like this exist for most CO isotopologues. They are summarized in detail in this section. Reports of laser-based measurements that were used to accurately calibrate our spectra often also presented an analysis of the rotational structure of the bands under study, providing associated data such as term values, reduced term values, and molecular constants. These results are also mentioned in detail in this section as they are compared later to our own results.Depending on the data available, laser...