Lamb dip of a Quadrupole Transition in H\(_2\)

The saturated absorption spectrum of the hyperfine-less S(0) quadrupole line in the (2-0) band of H\(_2\) is measured at \(\lambda=1189\) nm, using the NICE-OHMS technique under cryogenic conditions (72~K). It is for the first time that a Lamb dip of a molecular quadrupole transition is recorded. At...

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Bibliographic Details
Published in:arXiv.org 2023-03
Main Authors: Cozijn, F M J, Diouf, M L, Ubachs, W
Format: Article
Language:English
Subjects:
Absorption spectra
Quadrupoles
Recoil
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Summary:The saturated absorption spectrum of the hyperfine-less S(0) quadrupole line in the (2-0) band of H\(_2\) is measured at \(\lambda=1189\) nm, using the NICE-OHMS technique under cryogenic conditions (72~K). It is for the first time that a Lamb dip of a molecular quadrupole transition is recorded. At low (150-200 W) saturation powers a single narrow Lamb dip is observed, ruling out an underlying recoil doublet of 140 kHz. Studies of Doppler-detuned resonances show that the red-shifted recoil component can be made visible for low pressures and powers, and prove that the narrow Lamb dip must be interpreted as the blue recoil component. A transition frequency of 252\,016\,361\,164\,(8) kHz is extracted, which is off by -2.6 (1.6) MHz from molecular quantum electrodynamical calculations therewith providing a challenge to theory.
ISSN:2331-8422