Biomedical subjects

H R Jauslin

Publications and source records attributed to H R Jauslin.

6 recordsLinked to original sources

PubMed2005

Field-free two-direction alignment alternation of linear molecules by elliptic laser pulses.

We show that a linear molecule subjected to a short specific elliptically polarized laser field yields post-pulse revivals exhibiting alignment alternatively located along the orthogonal axis and the major axis of the ellipse. The effect is experimentally demonstrated by measuring the optical Kerr effect along two different axes. The conditions ensuring an optimal field-free alternation of high alignments along both directions are derived.

Journal Article↗

PubMed2005

Efficient and long-lived field-free orientation of molecules by a single hybrid short pulse.

We show that a combination of a half-cycle pulse and a short nonresonant laser pulse produces a strongly enhanced postpulse orientation. Robust transients that display both efficient and long-lived orientation are obtained. The mechanism is analyzed in terms of optimal oriented target states in finite Hilbert subspaces and shows that hybrid pulses can prove useful for other control issues.

Journal Article↗

PubMed2004

Control of localization and suppression of tunneling by adiabatic passage.

We show that a field of frequency omega combined with its second harmonic 2omega driving a double-well potential allows us to localize the wave packet by adiabatic passage, starting from the delocalized ground state. The relative phase of the fields allows us to choose the well of localization. We can suppress (and restore) the tunneling subsequently by switching on (and off) abruptly the fields at well-defined times. The mechanism relies on the fact that the dynamics is driven to an eigenstate of the Floquet Hamiltonian which is a localized state.

Journal Article↗

PubMed2003

Postpulse molecular alignment measured by a weak field polarization technique.

We report a direct nonintrusive observation of alignment and planar delocalization of CO2 after an intense linearly polarized femtosecond laser pulse excitation. The effects are measured by a polarization technique involving a perturbative probe that itself does not induce appreciable alignment. We show that this technique allows one to measure a signal proportional to -1/3, with theta the angle between the molecular axis and the laser polarization. Simulations that support this analysis allow one to characterize the experimentally observed alignment and planar delocalization quantitatively.

Journal Article↗

PubMed2002

Orientation of polar molecules by laser induced adiabatic passage.

We show that two overlapping linearly polarized laser pulses of frequencies omega and its second harmonic 2omega can strongly orient linear polar molecules, by adiabatic passage along dressed states. The resulting robust orientation can be interpreted as a laser-induced localization in the effective double well potential created by the fields, which induces a preliminary molecular alignment. The direction of the orientation can be selected by the relative phase of the fields.

Journal Article↗

PubMed1999

Approximate renormalization-group transformation for Hamiltonian systems with three degrees of freedom.

We construct an approximate renormalization transformation that combines Kolmogorov-Arnol'd-Moser and renormalization-group techniques, to analyze instabilities in Hamiltonian systems with three degrees of freedom. This scheme is implemented both for isoenergetically nondegenerate and for degenerate Hamiltonians. For the spiral mean frequency vector, we find numerically that the iterations of the transformation on nondegenerate Hamiltonians tend to degenerate ones on the critical surface. As a consequence, isoenergetically degenerate and nondegenerate Hamiltonians belong to the same universality class, and thus the corresponding critical invariant tori have the same type of scaling properties. We numerically investigate the structure of the attracting set on the critical surface and find that it is a strange nonchaotic attractor. We compute exponents that characterize its universality class.

Journal Article↗