High-precision spectroscopy of the HD+ molecule at the 1-p.p.b. level

J. Biesheuvel, J. Ph Karr, L. Hilico, K. S.E. Eikema, W. Ubachs, J. C.J. Koelemeij*

*Corresponding author for this work

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Recently we reported a high-precision optical frequency measurement of the (v, L): (0, 2) → (8, 3) vibrational overtone transition in trapped deuterated molecular hydrogen (HD+) ions at 10 mK temperature. Achieving a resolution of 0.85 parts-per-billion (p.p.b.), we found the experimental value [Ν 0 = 383, 407, 177.38 (41) MHz] to be in agreement with the value from molecular theory [Νth 383, 407, 177.150 (15) MHz] within 0.6 (1.1) p.p.b. (Biesheuvel et al. in Nat Commun 7:10385, 2016). This enabled an improved test of molecular theory (including QED), new constraints on the size of possible effects due to 'new physics,' and the first determination of the proton-electron mass ratio from a molecule. Here, we provide the details of the experimental procedure, spectral analysis, and the assessment of systematic frequency shifts. Our analysis focuses in particular on deviations of the HD+ velocity distribution from thermal (Gaussian) distributions under the influence of collisions with fast ions produced during (laserinduced) chemical reactions, as such deviations turn out to significantly shift the hyperfine-less vibrational frequency as inferred from the saturated and Dopplerbroadened spectrum, which contains partly unresolved hyperfine structure.

Original languageEnglish
Title of host publicationExploring the World with the Laser
Subtitle of host publicationDedicated to Theodor Hänsch on his 75th Birthday
EditorsDieter Meschede, Thomas Udem, Tilman Esslinger
Place of PublicationCham
PublisherSpringer International Publishing Switzerland
Number of pages41
ISBN (Electronic)9783319643465
ISBN (Print)9783319643458, 9783319877747
Publication statusPublished - 2018


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