Magnetic-Field Sensitive Line Ratios in EUV and Soft X-ray Spectra

We discovered a class of lines that are sensitive to the strength of the ambient magnetic field, and present a measurement of such a line in Ar IX near 49 A. Calculations show that the magnitude of field strengths that can be measured ranges from a few hundred gauss to several tens of kilogauss depending on the particular ion emitting the line

Ultrafast preparation and strong-field ionization of an atomic Bell-like state

Molecules are many body systems with a substantial amount of entanglement between their electrons. Is there a way to break the molecular bond of a diatomic molecule and obtain two atoms in their ground state which are still entangled and form a Bell-like state? We present a scheme that allows for the preparation of such entangled atomic states from single oxygen molecules on femtosecond time scales. The two neutral oxygen atoms are entangled in the magnetic quantum number of their valence electrons. In a time-delayed probe step, we employ non-adiabatic tunnel ionization, which is a magnetic quantum number-sensitive mechanism. We then investigate correlations by comparing single and double ionization probabilities of the Bell-like state. The experimental results agree with the predictions for an entangled state.Comment: 20 pages, 7 figures, 1 tabl

Soft-X-ray spectra of highly charged Os, Bi, Th, and U ions in an electron beam ion trap

Systematic variation of the electron-beam energy in an electron-beam ion trap has been employed to produce soft-X-ray spectra of Os, Bi, Th, and U with highest charge states ranging up to Ni-like ions. Guided by relativistic atomic structure calculations, the strongest lines have been identified with {Delta}n = 0 (n = 4 to n' = 4) transitions in Rb- to Cu-like ions. The rather weak 4p-4d transitions are much less affected by QED contributions than the dominant 4s-4p transitions. Our wavelength measurements consequently provide benchmarks with and (almost) without QED. Because the radiative corrections are not very sensitive to the number of electrons in the valence shell, our data, moreover, provide benchmarks for the evaluation of electron-electron interactions

Sideband Modulation by Sub-Cycle Interference

We experimentally and theoretically show that the electron energy spectra strongly depend on the relative helicity in highly intense, circularly polarized two-color laser fields which is an unexpected finding. The employed counter-rotating two-color (CRTC) fields and the co-rotating two-color (CoRTC) fields are both a superposition of circularly polarized laser pulses at a central wavelength of 390 nm and 780 nm (intensitiy ratio $I_{390}/I_{780}\approx 250$). For the CRTC field, the measured electron energy spectrum is dominated by peaks that are spaced by 3.18 eV (corresponds to the photon energy of light at a wavelength of 390 nm). For the CoRTC field, we observe additional energy peaks (sidebands). Using our semi-classical, trajectory-based models, we conclude that the sideband intensity is modulated by a sub-cycle interference, which sensitively depends on the relative helicity in circularly polarized two-color fields.Comment: 7 pages, 4 figure

L-Shell Spectroscopy of Au as a Temperature Diagnostic Tool

In order to develop plasma diagnostic for reduced-size hot hohlraums under laser irradiation, they have studied the L-shell emission from highly charged gold ions in the SuperEBIT electron beam ion trap. The resolving power necessary to identify emission features from individual charge states in a picket fence pattern has been estimated, and the observed radiation features have been compared with atomic structure calculations. They find that the strong 3d{sub 5/2} {yields} 2p{sub 3/2} emission features are particularly useful in determining the charge state distribution and average ion charge <Z>, which are strongly sensitive to the electron temperature