Biomedical subjects

Christoph H Keitel

Publications and source records attributed to Christoph H Keitel.

7 recordsLinked to original sources

PubMed2006

Nuclear quantum optics with x-ray laser pulses.

The direct interaction of nuclei with superintense laser fields is studied. We show that present and upcoming high-frequency laser facilities, especially together with a moderate acceleration of the target nuclei to match photon and transition frequency, do allow for resonant laser-nucleus interaction. These direct interactions may be utilized for the model-independent optical measurement of nuclear properties such as the transition frequency and the dipole moment, thus opening the field of nuclear quantum optics. As an ultimate goal, one may hope that direct laser-nucleus interactions could become a versatile tool to enhance preparation, control, and detection in nuclear physics.

Journal Article↗

PubMed2003

Lamb shift of laser-dressed atomic states.

We discuss radiative corrections to an atomic two-level system subject to an intense driving laser field. It is shown that the Lamb shift of the laser-dressed states, which are the natural state basis of the combined atom-laser system, cannot be explained in terms of the Lamb shift received by the atomic bare states which is usually observed in spectroscopic experiments. In the final part, we propose an experimental scheme to measure these corrections based on the incoherent resonance fluorescence spectrum of the driven atom.

Journal Article↗

PubMed2003

Phase control of collective quantum dynamics.

The manipulation of the steady-state behavior of a collection of dipole-interacting three-level atoms in a V or Lambda configuration is investigated as a function of the relative phase of two strong coherent driving fields. For larger samples, the phase is shown to be a convenient parameter to rapidly populate or depopulate completely a trapping state of the ensemble. As applications, we present the appropriately prepared atomic sample as an optical switching device and show its virtues in controlling the collective steady-state resonance fluorescence intensity.

Journal Article↗

PubMed2003

Quantum signatures in laser-driven relativistic multiple scattering.

The dynamics of an electronic Dirac wave packet evolving under the influence of an ultraintense laser pulse and an ensemble of highly charged ions is investigated numerically. Special emphasis is placed on the evolution of quantum signatures from single to multiple scattering events. We quantify the occurrence of quantum relativistic interference fringes in various situations and stress their significance in multiple-particle systems, even in the relativistic range of laser-matter interaction.

Journal Article↗

PubMed2003

Relativistic electron dynamics in intense crossed laser beams: acceleration and Compton harmonics.

Electron motion and harmonic generation are investigated in the crossed-beam laser-accelerator scheme in a vacuum. Exact solutions of the equations of motion of the electron in plane-wave fields are given, subject to a restricted set of initial conditions. The trajectory solutions corresponding to axial injection are used to calculate precise emission spectra. Guided by hindsight from the analytic investigations, numerical calculations are then performed employing a Gaussian-beam representation of the fields in which terms of order epsilon(5), where epsilon is the diffraction angle, are retained. Present-day laser powers and initial conditions on the electron motion that simulate realistic laboratory conditions are used in the calculations. The analytic plane-wave work shows, and the numerical investigations confirm, that an optimal crossing angle exists, i.e., one that renders the electron energy gain a maximum for a particular set of parameters. Furthermore, the restriction to small crossing angles is not made anywhere. It is also shown that energy gains of a few GeV and energy gradients of several TeV/m may be obtained using petawatt power laser beams.

Journal Article↗

PubMed2002

Spontaneous-emission suppression on arbitrary atomic transitions.

We propose a very simple scheme to slow down the usual exponential decay of upper state population in an atomic two-level system considerably. The scheme uses an additional possibly intense field with frequency lower than the total decay width of the atomic transition. This allows for additional decay channels with the exchange of one or more low-frequency photons during an atomic transition. These channels may then interfere with each other. The intensity and frequency of the low-frequency field are shown to act as two control parameters modifying duration and amount of the population trapping. An extension of the scheme to include transitions to more than one lower state is straightforward.

Journal Article↗

PubMed2002

Electron acceleration by a tightly focused laser beam.

State-of-the-art petawatt laser beams may be focused down to few-micron spot sizes and can produce violent electron acceleration as a result of the extremely intense and asymmetric fields. Classical fifth-order calculations in the diffraction angle show that electrons, injected sideways into the tightly focused laser beam, get captured and gain energy in the GeV regime. We point out the most favorable points of injection away from the focus, along with an efficient means of extracting the energetic electron with a static magnetic field.

Journal Article↗