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M Lezius

Publications and source records attributed to M Lezius.

8 recordsLinked to original sources
PubMed2004

Nonsequential double ionization at the single-optical-cycle limit.

We report differential measurements of Ar++ ion momentum distributions from nonsequential double ionization in phase-stabilized few-cycle laser pulses. The distributions depend strongly on the carrier-envelope (CE) phase. Via control over the CE phase one is able to direct the nonsequential double-ionization dynamics. Data analysis through a classical model calculation reveals that the influence of the optical phase enters via (i) the cycle dependent electric field ionization rate, (ii) the electron recollision time, and (iii) the accessible phase space for inelastic collisions. Our model indicates that the combination of these effects allows a look into single cycle dynamics already for few-cycle pulses.

Journal Article↗
PubMed2004

Gouy phase shift for few-cycle laser pulses.

We measured for the first time the influence of the Gouy effect on focused few-cycle laser pulses. The carrier-envelope phase is shown to undergo a smooth variation over a few Rayleigh distances. This result is of critical importance for any application of ultrashort laser pulses, including high-harmonic and attosecond pulse generation, as well as phase-dependent effects.

Journal Article↗
PubMed2003

Measurement of the phase of few-cycle laser pulses.

For the shortest pulses generated to date, the amplitude of the electromagnetic wave changes almost as rapidly as the field oscillates. The temporal variation of the field, which directly governs strong-field interactions, therefore depends on whether the maximum of the pulse amplitude coincides with that of the wave cycle or not, i.e., on the phase of the field with respect to the pulse envelope. It is demonstrated that the direction of electron emission from photoionized atoms can be controlled by varying the phase of the field, providing for the first time a tool for its accurate determination. Directing fast electron emission to the right or to the left with the light phase constitutes a new kind of coherent control.

Journal Article↗
PubMed2002

A B-TOF mass spectrometer for the analysis of ions with extreme high start-up energies.

Weak magnetic deflection is combined with two acceleration stage time-of-flight mass spectrometry and subsequent position-sensitive ion detection. The experimental method, called B-TOF mass spectrometry, is described with respect to its theoretical background and some experimental results. It is demonstrated that the technique has distinct advantages over other approaches, with special respect to the identification and analysis of very highly energetic ions with an initially large energy broadening (up to 1 MeV) and with high charge states (up to 30+). Similar energetic targets are a common case in intense laser-matter interaction processes found during laser ablation, laser-cluster and laser-molecule interaction and fast particle and x-ray generation from laser-heated plasma.

Journal Article↗
PubMed2001

Total, partial, and electron-capture cross sections for ionization of water vapor by 20-150 keV protons.

We present experimental results for proton ionization of water molecules based on a novel event by event analysis of the different ions produced (and lost). We are able to obtain mass analyzed product ion signals (e.g., H2O+, OH+, O+, O++, H+) in coincidence with the projectile analyzed after the collision, i.e., either being H+, neutral H after single electron capture during the ionization event, or H- after double electron capture. After proper calibration we are thus able to determine a complete set of cross sections for the ionization of a molecular target by protons including the total and the partial cross sections and in addition also the direct ionization and the electron capture cross sections.

Journal Article↗
PubMed2001

Nonadiabatic Multielectron Dynamics in Strong Field Molecular Ionization.

We report the observation of a general strong field ionization mechanism due to highly nonadiabatic multielectron excitation dynamics in polyatomic molecules. We observe that such excitation mechanisms greatly affect molecular ionization, fragmentation, and energetics. We characterized this phenomenon as a function of optical frequency, intensity, and molecular properties.

Journal Article↗
PubMed2001

Operating principle of an electron monochromator in an axial magnetic field.

Electron monochromators which are operated within an axial magnetic (guiding) field are especially suitable for the production of monochromatic electrons at low energies. Although in principle the technology of such devices has an appreciable historic background, we have discovered experimentally important new features, which cannot be understood using the previously published theories of operation. An in-depth study of the electron trajectories in a crossed electric and magnetic field using Simion1 showed a number of possible pitfalls, which have to be avoided in construction and operation. From our simulations we derived a novel design and operational method, which is currently under evaluation. We have already demonstrated that using this novel design an electron energy resolution of about 50 meV is realistic.

Electromagnetic Fields↗