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MO: Molekülphysik

MO 57: Poster: Cold Molecules

MO 57.2: Poster

Thursday, March 16, 2006, 16:30–18:30, Labsaal

Towards High Precision Spectroscopy of Ultracold Molecular Hydrogen Ions in a Linear Radiofrequency Trap — •Bernhard Roth, Heiner Daerr, Jeroen Koelemeij, Alexander Nevsky, and Stephan Schiller — Heinrich-Heine-Universität Düsseldorf

We have cooled the molecular hydrogen ions H₂⁺ and H₃⁺ and all their deuterated isotopomers (HD⁺, H₂D⁺, HD₂⁺, D₃⁺, D₂⁺, and D⁺) to translational temperatures in the 10 millikelvin range, by sympathetic cooling with laser-cooled beryllium ions, stored in a linear radiofrequency trap. The largest ion crystals contained more than 3000 well localized hydrogen molecules and up to 6000 ⁹Be⁺ ions. The mass ratio m_sc/m_lc of 0.2 between sympathetically cooled H₂⁺ and laser-cooled Be⁺ ions is the smallest achieved so far. The different ion species were detected mass-selectively by excitation of their trap oscillation modes. The observed crystal structures agree well with results from molecular dynamics simulations which were also used to deduce an indirect upper limit for their translational temperature.

Ultracold hydrogen molecules have the potential for precision tests of molecular structure theory, tests of Lorentz invariance, and measurements of electron and nuclear masses and their time variation. In particular, HD⁺ ions are of interest because they have dipole-allowed transitions.

Currently, we are performing 1+1 REMPI spectroscopy of ultracold HD⁺. The ro-vibrational overtone transitions v = 0 → v = 4 in HD⁺ at 1.4 µm will be excited and subsequently the excited molecules will be dissociated using an 266 nm-UV-laser. The disappearance rate of ultracold HD⁺ from the trap will be detected.