Five doctorates recently awarded at the MPSD

August 13, 2015

In the past few weeks, five doctoral students of the Max Planck Institute for the Structure and Dynamics of Matter defended their theses at the Universität Hamburg.

David Schmitz defended his thesis “Structural flexibility and chirality of polar molecules elucidated with broadband rotational spectroscopy” on 28 July. He joined the group of PD Melanie Schnell in 2011 and was her first doctoral student in Hamburg. He was also among the first doctoral students of the IMPRS-UFAST. During his PhD, he worked on the construction and subsequent operation of a broadband microwave spectrometer, the second in Europe. Using this spectrometer he explored the conformational flexibility of small organic molecules like menthone and menthol. Furthermore, he demonstrated microwave three-wave-mixing to differentiate between enantiomers using a broadband spectrometer.

Julian Hirscht defended his thesis “Femtosecond Electron Diffraction: Next generation electron sources for atomically resolved dynamics” on the 16th of July. He was the second doctoral student in the group of Prof. R. J. Dwayne Miller in Hamburg, which he joined in early 2010. During his work he developed large sections of the relativistic electron accelerator REGAE (Relativistic Electron Gun for Atomic Exploration), which targets electron pulse durations down to 25 femtoseconds and two compact electron diffraction setups for time-resolved studies of molecular dynamics with atomic resolution on the femtosecond timescale. The FED-CAMM (Femtosecond Electron Diffraction CAmera for Molecular Movies) can generate 105 electrons in pulses with duration of less than 100 femtoseconds at the specimen. The increase of the brightness and the improvements in the time resolution of the new electron sources allow the implementation of the long pursued goal of the observation of molecular dynamics with single electron pulses and indeed open up an electron bright future.

Rashmi Singla defended her thesis “Measuring correlated electron dynamics on few femtoseconds time scale” on 16 July 2015. She joined the group of Prof. Andrea Cavalleri in July 2010 and studied the temporal pathway of photo-induced phase transitions on time scales comparable to or shorter than the characteristic perturbation time. She studied photo-induced melting of orbital order in the transition metal oxide La0.5Sr1.5MnO4 with 4 femtosecond time resolution and a found temporal bottleneck. The work suggests the structural Jahn-Teller effect as the driving force for the stable orbital ordered state rather than the much faster electronic interactions. In a second experiment, she studied the dynamics of on-site correlations in the one-dimensional Mott insulator ET-F2TCNQ with 10 femtosecond near-single cycle infrared pulses. She found the exclusive modulation of effective Mottness at a frequency of 70 terahertz, twice the driving field frequency. This work suggests a quadratic coupling of the on-site correlation to the displacement coordinate of the excited molecule.

Matteo Mitrano defended his thesis “Nonequilibrium Emergent Phenomena in Organic Molecular Solids” on 15 July 2015. He joined the group of Prof. Andrea Cavalleri in November 2010 and worked on non-equilibrium dynamics of strongly correlated solids, with a particular focus on organic Mott insulators and superconductors. The main problem investigated during his studies is the control of photo-induced transient states by tuning microscopic electronic interactions in and out of equilibrium. In a first experiment on the Mott insulator ET-F2TCNQ, the pressure-induced changes in the ground state allowed to determine the influence of electronic correlations in defining the relaxation of photo-induced phases. A second experiment on the organic superconductor K3C60 led instead to the observation of a novel superconducting-like phase far above the equilibrium Tc as a consequence of resonant excitation of intramolecular vibrations.

Already on 29 June 2015, Ling Ren defended her thesis “Ultrafast Desorption Vibrational Excitation (DIVE): Applications Surgery, Mass Spectrometry and Towards Ultimate Limits in Biodiagnosis”. She joined the group of Prof. R. J. Dwayne Miller in November 2011 and was among the first doctoral students of the IMPRS-UFAST. She worked on the SUREPIRL project funded by an Advanced Grant of the European Research Council, in close collaboration with the University Medical Center Hamburg-Eppendorf and other institutes. She investigated the applications of the laser ablation performed by the picosecond infrared laser (PIRL) under the DIVE condition in medical and biological scenarios. She demonstrated that the PIRL ablation not only rendered precise and minimally invasive incisions for ophthalmologic purposes but also introduced protein species without fragmentation or chemical change to mass spectrometry analyses. One of the most prominent results of her work is that various biological complexes, from proteins to viruses and cells, can be extracted by the PIRL with preserved structure and functionality, and directly utilized for microscope imaging and biochemical analyses. This important feature of the PIRL extraction of biological entities shines light on the conspicuous potential of this technology in advancing rapid high-throughput biodiagnosis. In addition to her research, Ling Ren was also the representative of the doctoral students in the IMPRS-UFAST and the academic tutor of the MIN Faculty of the Universität Hamburg.

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