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arXiv · 2605.13060

Rotational energy levels in the ground vibrational state of methane with kHz-level accuracy from comb-referenced double-resonance and Lamb-dip spectroscopies

Vinicius Silva de Oliveira·Isak Silander·Hiroyuki Sasada·Sho Okubo·Hajima Inaba·Kevin K. Lehmann·Aleksandra Foltynowicz
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Abstract

Methane is a key spherical-top molecule, yet restrictive selection rules for one-photon transitions have prevented determination of its ground state (GS) energies with state-of-the-art kHz-level accuracy. We report the GS rotational energy level differences with kHz-level accuracy from two frequency-comb-referenced sub-Doppler methods: optical-optical double-resonance spectroscopy in the ${\Lambda}$-type configuration, and Lamb-dip spectroscopy of allowed and forbidden transitions. A Hamiltonian fit to the data yields GS term values with rotational numbers up to $\it{J}$ = 12 with kHz level accuracy.

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Vinicius Silva de Oliveira, Isak Silander, Hiroyuki Sasada, Sho Okubo, Hajima Inaba, Kevin K. Lehmann, Aleksandra Foltynowicz. 2026-05-13. Rotational energy levels in the ground vibrational state of methane with kHz-level accuracy from comb-referenced double-resonance and Lamb-dip spectroscopies. https://arxiv.org/abs/2605.13060

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