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DTSTAMP:20260202T062717
DTSTART;TZID=America/Detroit:20260225T150000
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SUMMARY:Workshop / Seminar:Department Colloquium | X-ray vision in the age of free-electron lasers: Making the invisible visible
DESCRIPTION:For well over a century x rays have been a powerful tool for probing atomic-scale structure due to their short wavelength and relatively weak interaction with matter.  As sources have become ever more brilliant\, scientists have been able to probe the microscopic world with more and more exquisite detail. In the past couple of decades free-electron lasers have provided the most intense laboratory source of x rays with femtosecond pulse durations---short enough to capture the fastest vibrations in solids\, and the making and breaking of chemical bonds.  In this colloquium\, I'll present a few examples of how we utilize these remarkable light sources to gain new insight into material properties.  I’ll present a novel method for studying non-equilibrium lattice dynamics in the time domain[1] which we’ve used to identify a novel lattice instability in photoexcited SnSe[2]\, as well as identify the changes in interatomic forces that drive it [3].  The high brightness further allows us to isolate valence electron density within the atomic bonds[4].  I’ll show how we’ve been able to view the local nonlinear response to sub-bandgap excitation in the prototypical semiconductor silicon[5].  These results advance our goals of developing a mechanistic understanding\, and novel methods of controlling\, the remarkable properties of materials on their fundamental length and time scales.\n\n[1] M. Trigo\, et al.\, Fourier-transform inelastic x-ray scattering from time- and momentum-dependent phonon-phonon correlations. Nat. Physics\, 9(12):790–794\, 2013.\n[2] Y. Huang\, et al.\, Observation of a novel lattice instability in ultrafast photoexcited SnSe. Phys. Rev. X\, 12(1):011029\, 2022.\n[3] Y. Huang\, et al.\, Nonthermal bonding origin of a novel photoexcited lattice instability in SnSe. Phys. Rev. Lett. 131:156902\, 2023\n[4] T. E. Glover\, et al.\, X-ray and optical wave mixing. Nature\, 488(7413):603–608\, 08 2012.\n[5] C. Ornelas-Skarin\, et. al.\, Second-order microscopic nonlinear optical susceptibility in a centrosymmetric material: Application to imaging valence electron motion. Phys. Rev. X\, 16:011006\, 2026.
UID:144106-21894670@events.umich.edu
URL:https://events.umich.edu/event/144106
CLASS:PUBLIC
STATUS:CONFIRMED
CATEGORIES:Physics,Science
LOCATION:West Hall - 340
CONTACT:
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DTSTAMP:20251202T115505
DTSTART;TZID=America/Detroit:20260225T150000
DTEND;TZID=America/Detroit:20260225T160000
SUMMARY:Other:Grants office hours: Get support applying for one of SSC's Sustainability Grants!
DESCRIPTION:Drop in to our weekly open office hours to learn and get support applying to our Planet Blue Student Innovation Fund (PBSIF) or Social and Environmental Sustainability Grant (SES).
UID:138848-21890501@events.umich.edu
URL:https://events.umich.edu/event/138848
CLASS:PUBLIC
STATUS:CONFIRMED
CATEGORIES:Environment,Sustainability
LOCATION:Off Campus Location
CONTACT:
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