RESUMO
The strong coupling between intense laser fields and valence electrons in molecules causes distortions of the potential energy hypersurfaces which determine the motion of the nuclei and influence possible reaction pathways. The coupling strength varies with the angle between the light electric field and valence orbital, and thereby adds another dimension to the effective molecular potential energy surface, leading to the emergence of light-induced conical intersections. Here, we demonstrate that multiphoton couplings can give rise to complex light-induced potential energy surfaces that govern molecular behavior. In the laser-induced dissociation of H2+, the simplest of molecules, we measure a strongly modulated angular distribution of protons which has escaped prior observation. Using two-color Floquet theory, we show that the modulations result from ultrafast dynamics on light-induced molecular potentials. These potentials are shaped by the amplitude, duration and phase of the dressing fields, allowing for manipulating the dissociation dynamics of small molecules.
RESUMO
Using H2+ and D2+, we observe two-surface population dynamics by measuring the kinetic energy of the correlated ions that are created when H2+ (D2+) ionize in short (40-140 fs) and intense (10(14) W/cm2) infrared laser pulses. Experimentally, we find a modulation of the kinetic energy spectrum of the correlated fragments. The spectral progression arises from a hitherto unexpected spatial modulation on the excited state population, revealed by Coulomb explosion. By solving the two-level time-dependent Schrödinger equation, we show that an interference between the net-two-photon and the one-photon transition creates localized electrons which subsequently ionize.
RESUMO
Non-Born-Oppenheimer supercomputer simulations of dissociative ionization of H2(+) with an ultrashort (t(p) < 15 fs), intense UV (lambda = 30, 60 nm) laser pulse are used to illustrate the imaging of nuclear motion. The resulting kinetic energy spectra of protons from Coulomb explosion lead by a simple inversion procedure to reconstruction of the initial nuclear probability distribution, i.e., laser Coulomb explosion imaging. Simultaneously, kinetic energy spectra of the ionized electron lead by energy conservation to the same reconstruction of the initial nuclear probability distribution, by laser photoelectron imaging.
RESUMO
Exact non-Born-Oppenheimer numerical solutions of the time-dependent Schrodinger equation for the 1D H+2 molecule in an intense, two-color (omega+2omega) laser field have been obtained. Both electron and proton kinetic energy spectra show spatial, correlated, asymmetric distributions. The calculated spectra exhibit the same unusual correlations as in experiments, in which both positively charged nuclear fragments and negatively charged photoelectrons were preferentially emitted in the same direction. The above asymmetries of photoemission of electrons seen in our quantum simulation are interpreted in the framework of a quasistatic tunneling model.
RESUMO
A treatment of a channel waveguide with a nonlinear, Kerr-type substrate is presented. A modified effective-index method was used to calculate mode indices and electric field distributions for the nonlinear waves.
RESUMO
A mode power measure is introduced to characterize optical slab waveguides with nonlinear substrate or cover. Together with the normalized film thickness and asymmetry coefficient, it allows for determining guiding properties in a way analogous to the description of Kogelnik and Ramaswamy for the linear waveguides and permits an easy interpretation and design of nonlinear slab waveguides. The universal dispersion curves for the TE modes are presented.
