Rydberg Spectroscopy Of Zeeman-decelerated Beams Of Metastable Helium Molecules

Jansen, Paul

Permalink

https://hdl.handle.net/2142/51038 Copy

Description

Title

Rydberg Spectroscopy Of Zeeman-decelerated Beams Of Metastable Helium Molecules

Author(s)

Jansen, Paul

Contributor(s)

• Merkt, Frederic
• Sprecher, Daniel
• Motsch, Michael

Issue Date

2014-06-19

Keyword(s)

Cold/Ultra-cold/Physics

Abstract

"Having three and four electrons, respectively, He$_2^+$ and He$_2$ represent systems for which highly accurate \textit{ab-initio} calculations might become feasible in the near future\footnote{W.-C. Tung, M. Pavanello, L. Adamowicz, \textit{J. Chem. Phys.} \textbf{136}, 104309 (2012).}. With the goal of performing accurate measurements of the rovibrational energy-level structure of He$_2^+$ by Rydberg spectroscopy of He$_2$ and multichannel quantum-defect theory extrapolation techniques\footnote{D. Sprecher, J. Liu, T. Kr\""ahenmann, M. Sch\""afer, and F. Merkt, \textit{J. Chem. Phys.} \textbf{140}, 064304 (2014).}, we have produced samples of helium molecules in the $a ^3\Sigma_\mathrm{u}^+$ state in supersonic beams with velocities tunable down to 100\,m/s by combining a cryogenic supersonic-beam source with a multistage Zeeman decelerator\footnote{M. Motsch, P. Jansen, J. A. Agner, H. Schmutz, and F. Merkt, \textit{arXiv:1401.7774}.}. The molecules are formed at an initial velocity of 500 m/s by striking a discharge in the pulsed expansion of helium gas from a reservoir kept at a cryogenic temperature of 10 K. Using rotationally-resolved PFI-ZEKE (pulsed-field-ionization zero-kinetic-energy) photoelectron spectroscopy, we have probed the rotational-state distribution of the molecules produced in the discharge and found vibrational levels up to $\nu'' = 2$ and rotational levels up to $N''=21$ to be populated. The molecular beam is coupled to a multistage Zeeman decelerator\footnote{N. Vanhaecke, U. Meier, M. Andrist, B. H. Meier, and F. Merkt, \textit{Phys. Rev. A} \textbf{75}, 031402(R) (2007).} that employs pulsed inhomogeneous magnetic fields to further reduce the beam velocity. By measuring the quantum-state distribution of the decelerated sample using photoelectron and photoionization spectroscopy we observed no rotational or vibrational state-selectivity of the deceleration process, but found that one of the three spin-rotation components of the He$_2$ $a ^3\Sigma_\mathrm{u}^+$ rotational levels is eliminated."

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51038

DOI

https://doi.org/10.15278/isms.2014.RH06

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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