Konstanz 1998 – scientific programme

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Q: Quantenoptik

Q 8: Nichtlineare Optik II

Q 8.2: Talk

Monday, March 16, 1998, 16:15–16:30, R 512

Production of continuous VUV radiation close to Lyman-α — •K. S. E. Eikema, J. Walz, and T. W. H"ansch — Max-Planck-Institut f"ur Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching

Coherent continuous radiation at Lyman-α (121.6 nm) is of increasing interest for precision spectroscopy of both hydrogen and antihydrogen. Radiation at Lyman-α allows for laser cooling on the 1S-2P transition with a recoil and Doppler limit of a few mK. Further, it is especially important for ultrahigh-resolution Laser spectroscopy on the 1S-2S transition with single atoms in a ‘shelving’ scheme.

We present the first demonstration of continuous vacuum ultraviolet (VUV) generation near Lyman-α based on four wave mixing in magnesium vapor. Radiation around 122.8 nm has been produced using two ultraviolet photons at 285 nm (from a frequency-doubled dye laser) and one infrared photon at 880 nm (from a Ti:Sapphire laser). These wavelengths allow for strong enhancement of the VUV yield by one- and two-photon resonance conditions in magnesium. At the three-photon level a very broad auto-ionizing state gives some enhancement as well. Extension of the generated wavelength to exactly Lyman-α is expected to be straightforward because of the weak wavelength dependence of this enhancement. Experiments to demonstrate this are in progress.