R. Moshammer

Determination of the carrier-envelope phase of few-cycle laser pulses with terahertz-emission spectroscopy

The availability of few-cycle optical pulses opens a window to physical phenomena occurring on the attosecond timescale. To take full advantage of such pulses, it is crucial to measure1,2,3,4 and stabilize1,2 their carrier-envelope (CE) phase, that is, the phase difference between the carrier wave and the envelope function. We introduce an approach to determine the CE phase by down-conversion of the laser light to the terahertz (THz) frequency range by means of plasma generation in ambient air, an isotropic medium where optical rectification (down-conversion) in the forward direction is only possible if the inversion symmetry is broken by electrical or optical means5,6,7,8,9,10. We show that few-cycle pulses directly produce a spatial charge asymmetry in the plasma. The asymmetry, associated with THz emission, depends on the CE phase, which allows determination of the phase by measurement of the amplitude and polarity of the THz pulse.

Time-Resolved Measurement of Interatomic Coulombic Decay in Ne2

The lifetime of interatomic Coulombic decay (ICD) [L. S. Cederbaum et al., Phys. Rev. Lett. 79, 4778 (1997)] in Ne2 is determined via an extreme ultraviolet pump-probe experiment at the Free-Electron Laser in Hamburg. The pump pulse creates a 2s inner-shell vacancy in one of the two Ne atoms, whereupon the ionized dimer undergoes ICD resulting in a repulsive Ne+(2p(-1))-Ne+(2p(-1)) state, which is probed with a second pulse, removing a further electron. The yield of coincident Ne+-Ne2+ pairs is recorded as a function of the pump-probe delay, allowing us to deduce the ICD lifetime of the Ne2(+)(2s(-1)) state to be (150±50)  fs, in agreement with quantum calculations.

X-Ray Diffraction from Isolated and Strongly Aligned Gas-Phase Molecules with a Free-Electron Laser

We report experimental results on x-ray diffraction of quantum-state-selected and strongly aligned ensembles of the prototypical asymmetric rotor molecule 2,5-diiodobenzonitrile using the Linac Coherent Light Source. The experiments demonstrate first steps toward a new approach to diffractive imaging of distinct structures of individual, isolated gas-phase molecules. We confirm several key ingredients of single molecule diffraction experiments: the abilities to detect and count individual scattered x-ray photons in single shot diffraction data, to deliver state-selected, e.g., structural-isomer-selected, ensembles of molecules to the x-ray interaction volume, and to strongly align the scattering molecules. Our approach, using ultrashort x-ray pulses, is suitable to study ultrafast dynamics of isolated molecules.

A 4π recoil-ion electron momentum analyzer: a high-resolution “microscope” for the investigation of the dynamics of atomic, molecular and nuclear reactions✩

Abstract A high-resolution recoil-ion momentum spectrometer based on a precooled localized supersonic jet target (COLTRIMS) has been combined with a novel low-energy electron analyzer with 4π solid angle for electrons with energies E e ≤ 30 eV including E e = 0 eV. Thus, three recoil-ion momentum components, the recoil-ion charge state and three momentum components of one electron emitted in any collision-induced ionization reaction are measured simultaneously with a coincidence efficiency of 28%. In order to accept large recoil-ion longitudinal momenta (along the beam) of p R ‖ ≤ 160 a.u. and simultaneously guarantee a superior resolution in this direction (Δ P R ‖ ≤ ± 0.08 a.u.), recoil ions are extracted in the longitudinal direction different from all former concepts. Test measurements, details on the present design and results of a kinematically complete experiment for single ionization are presented and possible further improvements are discussed. The future potential of such spectrometers for the investigation of collision-induced atomic many-particle reactions, the “Coulomb-explosion” of molecules and the spectroscopy of electronic states in heavy few-electron systems is illustrated. Similar techniques might be used to measure angular correlations and even the neutrino mass in β-decay experiments.

Observation of Bound-State beta- Decay of Fully Ionized Re-187: Re-187- Os-187 Cosmochronometry

We observed the bound-state

Correlated Multielectron Dynamics in Ultrafast Laser Pulse Interactions with Atoms

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Free-Electron Lasers: New Avenues in Molecular Physics and Photochemistry

decay of fully ionized

Imaging an aligned polyatomic molecule with laser-induced electron diffraction

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Attosecond tracing of correlated electron-emission in non-sequential double ionization

Re nuclei circulating in a storage ring. With two independent methods the time dependent growth of hydrogenlike

Non-linear processes in the interaction of atoms and molecules with intense EUV and X-ray fields from SASE free electron lasers (FELs)

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