12:30 - 12:50 Frank Cozijn - PhD Candidate, Quantum Metrology & Laser Applications, Vrije Universiteit Amsterdam
Lamb Dip of a Quadrupole Transition in H2
Abstract: The saturated absorption spectrum of the hyperfineless S(0) quadrupole line in the (2-0) band of H2 is measured at λ = 1189 nm, using the NICE-OHMS technique under cryogenic conditions (72 K). It is for the first time that a Lamb dip of a molecular quadrupole transition is recorded. At low (150-200 W) saturation powers a single narrow Lamb dip is observed, ruling out an underlying recoil doublet of 140 kHz. Studies of Doppler detuned resonances show that the red-shifted recoil component can be made visible for low pressures and powers, and prove that the narrow Lamb dip must be interpreted as the blue recoil component. A transition frequency of 252 016 361 164 (8) kHz is extracted, which is off by -2.6 (1.6) MHz from molecular quantum electrodynamical calculations therewith providing a challenge to theory.
12:50 -13:45 - Prof. Dr. Daniela Kraft, Leiden University
Designing reconfigurable colloidal structures: from powerful model systems to autonomous microscopic robots
Abstract: Many biological structures such as proteins and ion channels as well as machines and robots rely on changes in their shape to do useful work. Key to these shape changes is the presence of hinging elements that enable a reconfiguration of their conformation and the ability to consume energy. In this talk I will show how we realize flexible structures at the micrometer scale using micrometer-sized analogues of joints and hinges [1]. I will demonstrate their powerful model system character using micrometer-sized flexible chains [2,3], rings [4], and floppy lattices [5]. We find that thermal fluctuations, and thus entropy, together with their topology play a crucial role in shaping their conformations as well as their soft and stiff modes. I will demonstrate that we can realize unusual properties into colloidal structures by designing reconfiguration modes and in this way obtain the first colloidal versions of auxetic mechanical metamaterials. Finally, I will discuss how we can control and activate conformational changes to pave the way towards truly functional microstructures and autonomous microrobots.