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MO: Fachverband Molekülphysik
MO 12: High Resolution Spectroscopy and Precision Experiments
MO 12.6: Talk
Wednesday, March 13, 2019, 11:45–12:00, S HS 002 Biologie
Rotational spectroscopy of molecular ions with 3×10−12 resolution and 1×10−10 precision — Soroosh Alighanbari1, Gouri Giri1, Florin Constantin1,2, Michael Hansen1, Vladimir Korobov3, and •Stephan Schiller1 — 1Heinrich-Heine-Univ. Düsseldorf — 2PhLAM, Univ. Lille, Villeneuve d’Ascq — 3Joint Inst. for Nucl. Research, Dubna
Trapped and sympathetically laser cooled molecular ions can be spectroscopied with high spectral resolution. So far, however, the achieved linewidths were limited by the residual Doppler broadening present even at the mK - level temperatures reached in traps. In the case of rotational spectroscopy, with its large transition wavelengths, it is possible to take advantage of the confinement of the trapped ion ensemble in the directions transverse to the trap axis. It is then possible to reach the Lamb-Dicke regime, with a strong reduction in linewidth.
We demonstrate this on the molecular hydrogen ions HD+, whose fundamental rotational transition frequency is at 1.3 THz. We observe transition linewidths as small as 4 Hz. We fully resolve the hyperfine spectrum. We also measure the transition frequencies in absolute terms. We are then able to determine the precision of our technique by comparing the measured frequencies with the predictions from very accurate ab initio theory. We find agreement at the fractional level of 1×10−10. This represents the most accurate comparison of a molecular physics prediction with experiment.
Finally, we measure some hyperfine energies with lower experimental uncertainty than the theoretical prediction.