Simon: Controlling the XUV Transparency of Helium Using Two-Pathway Quantum Interference

Atoms irradiated with combined femtosecond laser and extreme ultraviolet (XUV) fields ionize through
multiphoton processes, even when the energy of the XUV photon is below the ionization potential.
However, in the presence of two different XUV photons and an intense laser field, it is possible to induce
full electromagnetic transparency. Taking helium as an example, the laser field modifies its electronic
structure, while the presence of two different XUV photons and the laser field leads to two distinct
ionization pathways that can interfere destructively. This work demonstrates a new approach for coherent
control in a regime of highly excited states and strong optical fields.

http://prl.aps.org/pdf/PRL/v106/i19/e193008

sildes here: http://charles.qols.ph.ic.ac.uk/~twitting/consJCDM/material/20120221_Simon/Journal%20Club%20IC%20Feb21%202012.pptx

Richard: Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser

Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser

http://www.nature.com/nature/journal/v481/n7382/abs/nature10721.html

Since the invention of the laser more than 50 years ago, scientists have striven to achieve amplification on atomic transitions of increasingly shorter wavelength1, 2, 3, 4, 5, 6, 7. The introduction of X-ray free-electron lasers8, 9, 10makes it possible to pump new atomic X-ray lasers11, 12, 13 with ultrashort pulse duration, extreme spectral brightness and full temporal coherence. Here we describe the implementation of an X-ray laser in the kiloelectronvolt energy regime, based on atomic population inversion and driven by rapid K-shell photo-ionization using pulses from an X-ray free-electron laser. We established a population inversion of the Kα transition in singly ionized neon14at 1.46 nanometres (corresponding to a photon energy of 849 electronvolts) in an elongated plasma column created by irradiation of a gas medium. We observed strong amplified spontaneous emission from the end of the excited plasma. This resulted in femtosecond-duration, high-intensity X-ray pulses of much shorter wavelength and greater brilliance than achieved with previous atomic X-ray lasers. Moreover, this scheme provides greatly increased wavelength stability, monochromaticity and improved temporal coherence by comparison with present-day X-ray free-electron lasers. The atomic X-ray lasers realized here may be useful for high-resolution spectroscopy and nonlinear X-ray studies.

Additional Info:

Jon's News&Views: http://www.nature.com/nature/journal/v481/n7382/full/481452a.html

Seb: Hollow core fiber at 1.8microns

Trallero-Herrero, C., Jin, C., Schmidt, B. E., Shiner, a D., Kieffer, J.-C., Corkum, P. B., Villeneuve, D. M., et al. (2012). Generation of broad XUV continuous high harmonic spectra and isolated attosecond pulses with intense mid-infrared lasers. Journal of Physics B: Atomic, Molecular and Optical Physics, 45(1), 011001. doi:10.1088/0953-4075/45/1/011001

paper: http://iopscience.iop.org/0953-4075/45/1/011001

Shiner, a. D., Schmidt, B. E., Trallero-Herrero, C., Wörner, H. J., Patchkovskii, S., Corkum, P. B., Kieffer, J.-C., et al. (2011). Probing collective multi-electron dynamics in xenon with high-harmonic spectroscopy. Nature Physics, 7(6), 464-467. Nature Publishing Group. doi:10.1038/nphys1940

paper: http://www.nature.com/nphys/journal/v7/n6/full/nphys1940.html

supplementary information (a lot of material): http://www.nature.com/nphys/journal/v7/n6/extref/nphys1940-s1.pdf

Slide material here: http://charles.qols.ph.ic.ac.uk/~twitting/consJCDM/material/20120131_Seb_1p8micronFibre/120131%20Xenon_1p8micron.pdf

DM/JC: Sid: Optical Thomson Scattering on MAGPIE Generator

slides are here: http://charles.qols.ph.ic.ac.uk/~twitting/consJCDM/material/20120124_sid_thomson/Optical%20Thomson%20Scattering%20on%20MAGPIE%20Generator.pptx

JC: Felix: Optimal pulse compression in long hollow fibers

Optimal pulse compression in long hollow fibers

by Nagy, Tamas, Vladimir Pervak, and Peter Simon

http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-36-22-4422

Felix's slides: http://charles.qols.ph.ic.ac.uk/~twitting/consJCDM/material/20120117_felix_fibre/optimal_pulse_compression_long_hollow_fibres.pptx
 

DM: Simon: XUV Initiated High Harmonic Generation

I intend on giving a thorough and descriptive introduction so if you'd like to learn more about what I'm trying to do in my project - this would be a good opportunity to find out! Also, if you think that your wisdom might add to the discussion, please come along - as I would value external insight.

DM: Suren: Attosecond cascades and time-delays in one-electron photo-ionization

I shall present time-resolved ab-initio study of the attosecond dynamics of electron-electron correlation during single-electron, single XUV-photon ionization of an excited two-electron atom. Specifically, we aim to time-resolve the two fundamental processes that play the key role in electronic excitations of the ion created by ionization: the shake-up and the post-ionization interaction of the outgoing electron with the core (knock-up). These two processes have different time characteristics: while the shake-up is an essentially instantaneous process, the knock-up excitation due to the interaction between the ionic and the continuum electrons depends on the movement of the latter and may be significant for longer times, leading to delays in the ionization process. We observe an interplay of the initial shake-up excitation with the excitation cascades induced by the post-ionization interaction of the outgoing electron with the core. The time-scales and the structure of these excitation cascades is directly linked to the time it takes the 'active' continuum electron, lifted from a deeper bound orbital, to traverse the orbit of the 'passive' electron residing in the outer orbit. Ideas for resolving and controlling the two-electron interaction dynamics during the ionization process will be discussed.