We report the most accurate measurement of the position of the weak quadrupole S(2) 2-0 line in D2. The spectra were collected with a frequency-stabilized cavity ring-down spectrometer (FS-CRDS) with an ultra-high finesse optical cavity (F = 637 000) and operating in the frequencyagile, rapid scanning spectroscopy (FARS) mode. Despite working in the Doppler-limited regime, we reached 40 kHz of statistical uncertainty and 161 kHz of absolute accuracy, achieving the highest accuracy for homonuclear isotopologues of molecular hydrogen. The accuracy of our measurement corresponds to the fifth significant digit of the leading term in QED correction. We observe 2.3σ discrepancy with the recent theoretical value. * mzab@doktorant.umk.pl † piotr.wcislo@fizyka.umk.pl
Close-coupling calculations of generalized spectroscopic cross-sections • Ab initio investigation of pressure broadening and shift coefficients • Ab initio investigation of Dicke parameters• Data for electric dipole R (j=0-5) and P (j=1-6) lines for purely rotational transitions, fundamental band and first four overtonesHighlights for Ab initio calculations of collisional line-shape parameters and generalized spectroscopic cross-sections for rovibrational dipole lines
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