Unidentified transitions in one-photon intrashell dynamics in Rydberg atoms

One-photon intrashell transitions in strongly driven Li (n = 25) atoms are studied experimentally. Thedegeneracy of the n shell is lifted by orthogonal dc electric and magnetic fields, which also define the eccentricity of the initial coherent elliptic state. The transitions are driven by a radio frequency pulse linearly polarized parallel to the major axis of the ellipse. A small dc electric field component parallel to the magnetic field splits the one-photon resonance into two, and transitions in between are studied by state-selective field ionization. Unexpected lines in the ionization spectra relating to unknown transitions are found and discussed.Fil: Preclíková, J.. University of Bergen; NoruegaFil: Waheed, A.. University of Bergen; NoruegaFil: Fregenal, Daniel Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; ArgentinaFil: Frette, Ø.. University of Bergen; NoruegaFil: Hamre, B.. University of Bergen; NoruegaFil: Hjertaker, B.T.. University of Bergen; NoruegaFil: Horsdal, E.. University Aarhus; DinamarcaFil: Pilskog, I.. University of Bergen; NoruegaFil: Førre, M.. University of Bergen; Norueg

Enhanced fluorescence of selected cationic dyes adsorbed on reduced-charge montmorillonite

The aggregation of three cationic dyes (CD), crystal violet (CV), Nile blue (NB) and rhodamine B (RB) in aqueous solution was studied by visible absorption spectrophotometry and compared with methylene blue (MB). The distribution of the dye species (monomers, dimers, trimers, and tetramers) in aqueous solutions with different concentrations of dye was calculated using equilibrium stepwise aggregation constants Kn. These cationic dyes were intercalated into montmorillonite (SAz-1) and its reduced charge form (RC-SAz(210)) prepared by heating lithium montmorillonite (Li/SAz-1) at 210ºC. The fluorescence of fully saturated CD/SAz and low-CD loaded CD/RC-SAz(210) complexes was studied. Visible absorption spectra of CD aqueous solutions and visible absorption spectra and X-ray diffraction patterns (d001) of the CD/SAz and CD/RCSAz(210) solid complexes were obtained and evaluated. Large fluorescence intensities were found for CV/RC-SAz(210) and NB/RC-SAz(210) complexes in the same way as for the complex of methylene blue with reduced-charge montmorillonite MB/RCM(210) described previously

State-selective Rydberg excitation with femtosecond pulses

We show that multipulse excitation of Rydberg atoms with a sequence of short time-delayed femtosecond pulses results in strong n selection of the final-state amplitudes. In the experiment, a 150 fs laser pulse, which alone populates n levels from 22–32 in Li, is chopped into four time-delayed excitation pulses, which results in a strong modification of the n-level distribution. The mechanism demonstrated in the experiment is derived theoretically: With more pulses, it is shown that the population of a single or a few n levels can be performed on demand and varied as long as the central laser frequency is given.Fil: Kozák, M.. Charles University; República ChecaFil: Preclíková, J.. University Of Bergen; NoruegaFil: Fregenal, Daniel Eduardo. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hansen, J. P.. University Of Bergen; Norueg

Spatially and spectrally resolved quantum path interference with chirped driving pulses.

We measure spectrally and spatially resolved high-order harmonics generated in argon using chirped multi-cycle laser pulses. Using a stable, high-repetition rate laser we observe detailed interference structures in the far-field. The structures are of two kinds; off-axis interference from the long trajectory only and on-axis interference including the short and long trajectories. The former is readily visible in the far-field spectrum, modulating both the spectral and spatial profile. To access the latter, we vary the chirp of the fundamental, imparting different phases on the different trajectories, thereby changing their relative phase. Using this method together with an analytical model, we are able to explain the on-axis behaviour and access the dipole phase parameters for the short (${\alpha }_{{\rm{s}}}$) and long (${\alpha }_{{\rm{l}}}$) trajectories. The extracted results compare very well with phase parameters calculated by solving the time-dependent Schrödinger equation. Going beyond the analytical model, we are also able to successfully reproduce the off-axis interference structure

Photophysics of nanostructured metal and metal-contained composite films

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