Homepage for the Landahl Research Group

My research interest is the measurement and control of transient phenomena at atomic time-scales and length-scales.  The major questions that motivate my research are:

1.    How does a system approach equilibrium after sudden pertubation?
2.    Can intermediate states be manipulated in real time to alter outcomes?
3.    What new exotic behaviors can be identified under transient conditions?

I seek to answer these questions by making molecular movies – recording events with very high spatial resolution and a very fast shutter speed.   Tools used in my research include ultrafast lasers and synchrotron x-rays, used either alone or in combination. 

Please visit the links to the left for more information.  I am located at the DePaul University Physics Department.  You can view my cv or email me:  elandahl@depaul.edu .

Also:  Read about me as the Dancing Physicist!

Science Highlight

Watching nonlinear optics happen inside a semiconductor

G. Jackson Williams, Sooheyong Lee, Donald A. Walko, Michael A. Watson, Wonhuyk Jo, Dong Ryeol Lee and Eric C. Landahl,  "Direct measurements of multi-photon induced nonlinear lattice dynamics in semiconductors via time-resolved x-ray scattering,"  Scientific Reports 6, 39506 (2016).  doi:10.1038/srep39506  

Usually light travels independent of other light.  (For instance, room lights or laser beams pass right through each other.)  If light beams are intense enough however beams can interact with each other through​ a material:. light can cause itself to bend, absorb, or change color.  These are examples of "nonlinear optics", phenomena that are being used to build faster computers, more efficient lighting, and better microscopes.   This new paper shows how the materials that enable these reactions themselves respond.

Figure 1

(a) Experimental schematics for the Time-resolved X-ray scattering measurement. (b) Bragg diffraction rocking curves at various laser fluences (vertically offset) at Δt = 700 ps are fitted to Gaussian distribution. (c) Mean lattice displacements, which are obtained by converting Θ − ΘB into Δd via Bragg’s law, along [004] reflection at Δt = 700 ps after the laser for varying laser fluences. The transient lattice response can be divided into three distinct regimes as the function of incident laser fluence, (i) linear expansion of the crystal, (ii) saturation of the linear response, and (ii) reoccurrence of a linear-like expansion at the highest fluences.