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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
Subject(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.
Issue Date:06/21/18
Publisher:International Symposium on Molecular Spectroscopy
Citation Info:APS
Genre:Conference Paper / Presentation
Type:Text
Language:English
URI:http://hdl.handle.net/2142/100576
DOI:10.15278/isms.2018.RG08
Other Identifier(s):RG08
Date Available in IDEALS:2018-08-17
2018-12-12


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