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 Title: Spectroscopy of H2+ and HD+ near the dissociation threshold: shape and feshbach resonances Author(s): Merkt, Frederic Contributor(s): Beyer, Maximilian Subject(s): Spectroscopy of Large Amplitude Motions Abstract: \begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.30]{maby_ortho_h2-01.eps} \end{wrapfigure} We use high Rydberg states to measure the properties of H$_2^+$ and HD$^+$ in the vicinity of their dissociation limits H$^+$+H, H$^+$+D and H+D$^+$, with particular emphasis on quasibound rovibrational levels above the dissociation threshold of the X$^+$ $^2\Sigma_g^+$ ground state. Although the existence of these quasibound levels has been predicted a long time ago, they have never been observed. Positions and widths of the lowest resonances have not been calculated either. Given the role that such states play in the three-body and radiative recombination of H(1s) and H$^+$ to form H$_2^+$, this lack of data may be regarded as one of the largest unknown aspects of this otherwise accurately known fundamental molecular cation. We present measurements of the positions and widths of the lowest-lying quasibound rotational levels (shape resonances) of H$_2^+$, located close to the top of the centrifugal barriers and which decay by quantum-mechanical tunneling. For HD$^+$ we present measurements of rovibrational levels of the A$^+$ $^2\Sigma_u^+$ state, located between the two dissociation limits. Because of the g-u-symmetry breaking in HD$^+$, these levels are coupled to the H$^+$+D continuum by nonadiabatic interactions (Feshbach resonances). The experimental results will be compared with the positions and widths we calculate for these levels using a potential model for the X$^+$ and the A$^+$ state of H$_2^+$ and HD$^+$ which includes adiabatic, nonadiabatic, relativistic and radiative corrections to the Born-Oppenheimer potential energies. Issue Date: 2016-06-20 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: En URI: http://hdl.handle.net/2142/91252 Rights Information: Copyright 2016 by the authors Date Available in IDEALS: 2017-01-26
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