High-resolution Laser Spectroscopy Of The Rydberg Stark Manifold In H2

Hölsch, Nicolas

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https://hdl.handle.net/2142/116864 Copy

Description

Title

High-resolution Laser Spectroscopy Of The Rydberg Stark Manifold In H2

Author(s)

Hölsch, Nicolas

Contributor(s)

• Merkt, Frédéric
• Doran, Ioana

Issue Date

2022-06-20

Keyword(s)

Comparing theory and experiment

Abstract

From the precise measurement of the ionization energy of H$_2$ its dissociation energy can be determined\footnote{N. H\"olsch, M. Beyer, E.J. Salumbides, K.S.E. Eikema, W. Ubachs, Ch. Jungen, and F. Merkt, Phys. Rev. Lett., 122(10), 103003 (2019)}, which serves as a benchmark quantity for QED calculations\footnote{M. Puchalski, J. Komasa, P. Czachorowski, and K. Pachucki, Phys. Rev. Lett., 122(10), 103003 (2019)}. The most precise determinations of the ionization energies of molecular hydrogen currently rely on the extrapolation of Rydberg series using multichannel quantum-defect theory (MQDT)\footnote{D. Sprecher, Ch. Jungen and F. Merkt, J. Chem. Phys. 140, 104303:1-18 (2014)}. Nonpenetrating high-$\ell$ states offer significant advantages for these extrapolations: they have small quantum defects and are much less perturbed by channel interactions than low-$\ell$ states. Their high polarisabilities are a disadvantage in zero-field measurements, but can be exploited to our advantage in Stark measurements. We show that the combination of a 3-photon excitation scheme with application of relatively weak electric fields (10 - 250~mV/cm) provides easy optical access to the linear Stark manifolds associated with near-degenerate high-$\ell$ states. We perform spectroscopy of the high-Rydberg Stark manifold with both continuous-wave millimeter-wave and near-infrared (NIR) radiation. The manifold states are desirable as spectroscopic targets because their positions are less sensitive to errors in the quantum defects, a limiting factor in the determination of ionization energies by Rydberg series extrapolation. Extrapolating the linear Stark manifold to zero field yields accurate values of the zero-quantum-defect positions, given by $-\mathcal{R}_{\mathrm{H}_2}/n^2$ relative to the ionization thresholds. These positions constitute references for the respective $\ell=3$ states and provide an assessment of multichannel-quantum-defect-theory calculations at a precision on the order of 100~kHz. We show that this method can contribute to a one-order-of-magnitude improvement in the determination of ionization energies in molecular hydrogen and that, by using narrow-band NIR laser light, it can be extended beyond the ground state of para-H$_2^+$.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116864

DOI

https://doi.org/10.15278/isms.2022.MJ09

Copyright and License Information

Copyright 2022 held by the authors

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