VUV Spectroscopic Study of the D1[Pi]u State of Molecular Deuterium

• Published in: Molecular physics 2011-11, Vol.109 (22), p.2693
• Main Authors: Dickenson, G D, Ivanov, T I, Ubachs, W, Roudjane, M, de Oliveira, N, Joyeux, D, Nahon, L, Tchang-Brillet, W-UL, Glass-Maujean, M, Schmoranzer, H, Knie, A, Kubler, S, Ehresmann, A
• Format: Article
• Language: English
• Subjects: Symmetry
• ISSN: 0026-8976; 1362-3028
• DOI: 10.1080/00268976.2011.631056

The D1Πu- [image omitted] absorption system of molecular deuterium has been re-investigated using the VUV Fourier-Transform (FT) spectrometer at the DESIRS beamline of the synchrotron SOLEIL and photon-induced fluorescence spectrometry (PIFS) using the 10 m normal incidence monochromator at the synchrotron BESSY II. Using the FT spectrometer absorption spectra in the range 72-82 nm were recorded in quasi static gas at 100 K and in a free flowing jet at a spectroscopic resolution of 0.50 and 0.20 cm-1 respectively. The narrow Q-branch transitions, probing states of Π- symmetry, were observed up to vibrational level v = 22. The states of Π+ symmetry, known to be broadened due to predissociation and giving rise to asymmetric Beutler-Fano resonances, were studied up to v = 18. The 10 m normal incidence beamline setup at BESSY II was used to simultaneously record absorption, dissociation, ionization and fluorescence decay channels from which information on the line intensities, predissociated widths, and Fano q-parameters were extracted. R-branch transitions were observed up to v = 23 for J = 1-3 as well as several transitions for J = 4 and 5 up to v = 22 and 18 respectively. The Q-branch transitions are found to weakly predissociate and were observed from v = 8 to the final vibrational level of the state v = 23. The spectroscopic study is supported by two theoretical frameworks. Results on the Π- symmetry states are compared to ab initio multi-channel-quantum defect theory (MQDT) calculations, demonstrating that these calculations are accurate to within 0.5 cm-1. Furthermore, the calculated line intensities of Q-lines agree well with measured values. For the states of Π+ symmetry a perturbative model based on a single bound state interacting with a predissociation continuum was explored, yielding good agreement for predissociation widths, Fano q-parameters and line intensities.