K. Winkler

Dye laser saturation spectroscopy of the 23S1-23P transition in6, 7Li+ ions

The metastable 23S1 state and the short lived 23P states of the helium-like6, 7Li+ ion spectra have been investigated by dye laser saturation spectroscopy in a low-energy Li+ ion-beam and fluorescence light detection. The hyperfine structure splittings of all the levels, the 23P fine structure intervals and the isotope shift of the 23S1-23P transitions have been measured. These measurements were made by application of a specially constructed tunable dye laser system capable of single-mode laser scans over more than 60 GHz.

Laser-microwave spectroscopy of lithium ions: 23S1 hyperfine structure of7Li+

The hyperfine structure (hfs) splittings of the metastable 1s2s3S1 state of7Li+ have been measured with combined laser optical pumping and microwave resonance. A lowenergy Li+ ion beam, optically excited by an intersecting laser beam, passed a waveguide where radio frequency transitions were induced. The resulting population transfer among the hfs levels of the3S1 was detected via the change in intensity of the fluorescence light from a second crossing region of laser light and ion beam located past the waveguide. The magnetic hfs constantA(7Li+, 1s2s3S1) was measured and compared with theory. A deviation of the two transition frequenciesν(F=3/2−F=5/2) andν(F=1/2−F=3/2) from the interval rule is due to a depression of theF=3/2 hfs sublevel, caused by mixing of the 23S1 and 21S0 states via hyperfine interaction. This shift was never observed so far in a two-electron spectrum, because of absence ofI>1/2 isotopes in He, the only two-electron atom investigated spectroscopically with high precision. The size of the shift is in fair agreement with a theoretical estimate.

Two-photon intracavity dye laser spectroscopy of the 4S and 3D term in6, 7Li

Doppler-free two-photon spectroscopy of several states of6, 7Li has been achieved by placing an atomic beam inside the dye laser cavity. The hyperfine structure splitting of the 4S state, the fine structure splitting of the 3D level as well as the isotope shifts of the 2S–4S and 2S-3D transition have been measured, by scanning the single-mode laser frequency and detecting the fluorescence light. In addition, signal detection by three-photon ionization via the resonant 3D state was accomplished.

Laser-Microwave Spectroscopy of Li+ Ions

The Li+ ion, a two-electron system like He is of fundamental interest as a testing ground for atomic structure theory. This paper reports on combined laser-microwave measurements of hyperfine structure (hfs) splittings of the metastable (τ ≈ 50 sec) ls2s 3S1 state in 6,7Li+ and of the short-lived (τ ≈ 43 nsec) ls2p 3P multiplet in 7Li+. The precise data from this experiment should stimulate improved ab initio calculations of the 2 3S1 hfs not available yet. It is also an aim of this experiment to test the very precise theoretical hfs [1] and fine structure [2] values existing for the 2 3P states. For very accurate 2 3P fine structure measurements in 4He see [3].