FINE STRUCTURE OF METASTABLE 4He2 USING ZEEMAN-DECELERATED MOLECULAR-BEAM RESONANCE SPECTROSCOPY

Semeria, Luca

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https://hdl.handle.net/2142/100576 Copy

Description

Title

FINE STRUCTURE OF METASTABLE 4He2 USING ZEEMAN-DECELERATED MOLECULAR-BEAM RESONANCE SPECTROSCOPY

Author(s)

Semeria, Luca

Contributor(s)

• Merkt, Frederic
• Schmutz, Hansjürg
• Agner, Josef A.
• Jansen, Paul

Issue Date

06/21/18

Keyword(s)

Cold and ultracold molecules

Abstract

The $a\,^3\Sigma_u^+$ state of $^{4}$He$_{2}$ is a metastable state with a lifetime of about $18$\,s. The spin-spin and spin-rotation interactions result in a splitting of each rotational level $N$ into three components $J=N, N\pm1$. The fine structure intervals of the $N=1$, $3$, $5$, $7 - 11$ and $25$ - $29$ have been measured by radio frequency (rf) spectroscopy\footnote{W. Lichten, M.V. McCusker and T. L. Vierima, \textit{J. Chem. Phys.}, \textbf{61}, 2200 (1974).} \footnote{W. Lichten and T. Wik, \textit{J. Chem. Phys.}, \textbf{69}, 98 (1978).} \footnote{M. Kristensen and N. Bjerre, \textit{J. Chem. Phys.}, \textbf{93}, 983 (1990).} \footnote{I. Hazell, A. N\o rregaard and N. Bjerre, \textit{J. Mol. Spectrosc.}, \textbf{172}, 135 (1995).} and were included in a global analysis of the $a\,^3\Sigma_u^+$ state \footnote{C. Focsa, P. F. Bernath and R. Colin, \textit{J. Mol. Spectrosc.}, \textbf{191}, 209, (1998).}. A new measurement of the fine structure of all rotational levels between $N=1$ and $21$ of the $a\,^3\Sigma_u^+$ ($v=0$) state will be presented. The $J=N$ fine-structure components, which are high-field seeking in magnetic fields, have been eliminated using a multistage Zeeman decelerator, and repopulated from the low-field-seeking $J=N\pm1$ components using rf radiation prior to detection by excitation to Rydberg states followed by pulsed-field ionization. The low velocity of the Zeeman decelerated beam\footnote{M. Motsch, P. Jansen, J. A. Agner, H. Schmutz and F. Merkt, Phys. Rev. A, \textbf{89}, 043420 (2014).} \footnote{P. Jansen, L. Semeria, L. E. Hofer, S. Scheidegger, J. A. Agner, H. Schmutz and F. Merkt, \textit{Phys. Rev. Lett.}, \textbf{115}, 133202 (2015).} enabled long interaction times of the molecules with the rf radiation and therefore a reduction of the transit-time broadening down to 10 kHz (FWHM), allowing the transition frequencies to be determined very accurately. The fine structure has been analyzed using an effective Hamiltonian to obtain improved values of the spin-spin and spin-rotation coupling constants for the $a\,^3\Sigma_u^+$ ($v=0$) metastable state of $^{4}$He$_{2}$, including centrifugal distortion corrections.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/100576

DOI

10.15278/isms.2018.RG08

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