9/5-2017 Taran Journal Club Partial Covariance Mapping for the Structural Analysis of Biomolecules

2/5-2017 Morgane: Electron Dynamics upon Ionization of Polyatomic Molecules: Coupling to Quantum Nuclear Motion and Decoherence

Knowledge about the electronic motion in molecules is essential for our understanding of chemical reactions and biological processes. The advent of attosecond techniques opens up the possibility to induce electronic motion, observe it in real time, and potentially steer it. A fundamental question remains the factors influencing electronic decoherence and the role played by nuclear motion in this process. Here, we simulate the dynamics upon ionization of the polyatomic molecules paraxylene and modified bis-methylene-adamantane, with a quantum mechanical treatment of both electron and nuclear dynamics using the direct dynamics variational multiconfigurational Gaussian method. Our simulations give new important physical insights about the expected decoherence process. We have shown that the decoherence of electron dynamics happens on the time scale of a few femtoseconds, with the interplay of different mechanisms: the dephasing is responsible for the fast decoherence while the nuclear overlap decay may actually help maintain it and is responsible for small revivals.

25/04-2017 Margarita: High-order optical processes in intense laser field: Towards nonpertubative nonlinear optics

https://doi.org/10.1103/PhysRevA.93.053812

4/4-2017 [Provisional] Susan

28/3-2017 Tom Journal Club on double on ionization of molecules with attosecond pulses

14/3-2017 Daniel Schade: Reddragon booster amplifier

7/3-2017 Gediminas: Liquid jets are awesome

A time-resolved study of ultrafast phenomena in liquids is a very challenging yet potentially rewarding scientific goal. Circular liquid jets have been used in vacuum as targets for photoelectron spectroscopy [1-2] or alternatively thin-walled cells are used for X-rays absorption experiments [3]. Here we describe an alternative approach: a time-resolved soft X-rays absorption experiment using a thin liquid sheet target in vacuum to minimise absorption of soft X-rays in normal atmosphere or cell windows. The liquid sheet targets for transient absorption experiments have to be optically flat, very thin (on the order of few μm), stable and compatible with kHz light sources to achieve good signal-to-noise ratio. Optically flat liquid targets able to operate in vacuum would also have scope for many other applications: i) laser proton acceleration, ii) plasma mirrors for contrast enhancement or iii) timing tools for XFEL experiments. Colliding circular jet technology for the generation of flat liquid sheets is a potential solution to the problem [4] but can be expensive and difficult to use in practice due to a requirement to maintain alignment of two circular jets very precisely at a specific angle in vacuum. We propose to use a single-nozzle design, which completely eliminates this alignment problem. High stability, optically flat and very thin 1.6±0.1 μm liquid jet sheet targets of isopropanol were achieved in normal atmosphere (see Figure 1) and in medium vacuum (5×10-1 mbar) by using an innovative high resolution 3D-printed nozzles.

Figure 1: Liquid jet flow in normal atmosphere. Interference fringes of the jet were recorded by illuminating liquid jet with He-Ne laser.

Acknowledgments: This work was support by EPSRC Grant EP/I032517/1. The author would like to acknowledge Dr. Avi Braun (and Nanoplasmonics group) for training and access to 3D printer.


References
[1] B. Winter, M. Faubel, Chem. Rev. 2006, 106, 1176-1211.
[2] T. Gladytz, B. Abel, K. R. Siefermann, Phys. Chem. Chem. Phys.2015, 17, 4926-4936.
[3] J. J. Velasco-Velez, C. H. Wu, T. A. Pascal, L. F. Wan, J. Guo, D. Prendergast, and M. Salmeron, Science 2014, 346, 831-834.
[4] M. Ekimova, W. Quevedo, M. Faubel, P. Wernet, E. T. J. Nibbering, Struct. Dyn. 2015, 2, 0543101.