Studies of Metastable Rydberg States of Atoms and Molecules Using Coherent XUV Radiation

Wolfgang Ernst, T. P. Softley, Richard N. Zare

Hideaki Sakai, K. Miyazaki

Xiaobo Xie, Ting Sun

The investigation of spectroscopy of vacuum ultraviolet (VUV, 100-200 nm) and extreme ultraviolet (XUV, 10-100 nm) regions has attracted the attention of many researchers in recent years because of its promising applications in such areas as spectroscopy of highly excited states of atoms and molecules, life science, plasma physics and material science. In this paper we report the study of molecular coherent spectrum in the VUV and XUV regions through nonlinear optical processes and the determination of the rotational temperature of molecules. Because molecular gases have abundant energy levels, it can provide resonant levels to enhance the generated radiation and a wide tunibility of the spectrum in VUV and XUV regions. The determination of the rotational temperature of molecules will be very useful for the study of molecular spectroscopy and the nonlinear optical process in VUV/XUV regions.

Eugene Oks

T. Thiele, Stefan Filipp, Josef A. Agner +6 more

Helium atoms in Rydberg states have been manipulated coherently with microwave radiation pulses near a gold surface and near a superconducting NbTiN surface at a temperature of $3\phantom{\rule{0.28em}{0ex}}\mathrm{K}$. The experiments were carried out with a skimmed supersonic beam of metastable ${(1s)}^{1}{(2s)}^{1}\phantom{\rule{0.28em}{0ex}}{}^{1}{S}_{0}$ helium atoms excited with laser radiation to $np$ Rydberg levels with principal quantum number $n$ between 30 and 40. The separation between the cold surface and the center of the collimated beam is adjustable down to $250\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\mathrm{m}$. Short-lived $np$ Rydberg states were coherently transferred to the long-lived $ns$ state to avoid radiative decay of the Rydberg atoms between the photoexcitation region and the region above the cold surfaces. Further coherent manipulation of the $ns$ Rydberg states with pulsed microwave radiation above the surfaces enabled measurements of stray electric fields and allowed us to study the decoherence of the atomic ensemble. Adsorption of residual gas onto the surfaces and the resulting slow buildup of stray fields was minimized by controlling the temperature of the surface and monitoring the partial pressures of ${\mathrm{H}}_{2}\mathrm{O}$, ${\mathrm{N}}_{2}$, ${\mathrm{O}}_{2}$, and $\mathrm{C}{\mathrm{O}}_{2}$ in the experimental chamber during the cool-down procedure. Compensation of the stray electric fields to levels below $100\phantom{\rule{0.28em}{0ex}}\mathrm{mV}/\mathrm{cm}$ was achieved over a region of $6\phantom{\rule{0.28em}{0ex}}\mathrm{mm}$ along the beam-propagation direction which, for the $1770\text{-m}/\mathrm{s}$ beam velocity, implies the possibility to preserve the coherence of the atomic sample for several microseconds above the cold surfaces.

Gerard T. Higgins