Journal article
VUV Spectroscopic Study of the D¹Π_{u} State of Molecular Deuterium
Publication Details
Authors:  Dickenson, G.; Ivanov, T.; Ubachs, W.; Roudjane, M.; de Oliveira, N.; Joyeux, D.; Nahon, L.; TchangBrillet, W.; GlassMaujean, M.; Schmoranzer, H.; Knie, A.; Kübler, S.; Ehresmann, A.

Journal:  Molecular Physics 
Abstract
The D ^{1}Π^{}_{u} absorption system of molecular deuterium has been reinvestigated using the VUV FourierTransform (FT) spectrometer at the DESIRS beamline of the synchrotron SOLEIL and photoninduced fluorescence spectrometry (PIFS) using the 10 m normal incidence monochromator at the synchrotron BESSY II. Using the FT spectrometer absorption spectra in the range 7282 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 Qbranch 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 BeutlerFano 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 qparameters were extracted. Rbranch transitions were observed up to v = 23 for J = 13 as well as several transitions for J = 4 and 5 up to v = 22 and 18 respectively. The Qbranch 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 multichannelquantum defect theory (MQDT) calculations, demonstrating that these calculations are accurate to within 0.5 cm^{1}. Furthermore, the calculated line intensities of Qlines 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 qparameters and line intensities.