Ultrahigh finesse cavity-enhanced spectroscopy for accurate tests of quantum electrodynamics for molecules
Mikołaj Zaborowski, Michał Słowiński, Kamil Stankiewicz, Franck Thibault, Agata Cygan, Hubert Jóźwiak, Grzegorz Kowzan, Piotr Masłowski, Akiko Nishiyama, Nikodem Stolarczyk, Szymon Wójtewicz, R. Ciuryło, Daniel Lisak, Piotr Wcisło
Abstract
. The spectra were collected with a frequency-stabilized cavity ringdown spectrometer (FS-CRDS) with an ultrahigh finesse optical cavity ($ {\cal F} = 637 000 $F=637000) and operating in the frequency-agile, 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 quantum electrodynamics (QED) correction. We observe $ 2.3\sigma $2.3σ discrepancy with the recent theoretical value.