{ "144106-21894670": { "datetime_modified":"20260202T062717", "datetime_start":"20260225T150000", "datetime_end":"20260225T160000", "has_end_time":1, "date_start":"2026-02-25", "date_end":"2026-02-25", "time_start":"15:00:00", "time_end":"16:00:00", "time_zone":"America\/Detroit", "event_title":"Department Colloquium | X-ray vision in the age of free-electron lasers: Making the invisible visible", "occurrence_title":"", "combined_title":"Department Colloquium | X-ray vision in the age of free-electron lasers: Making the invisible visible: David A. Reis (Stanford PULSE Institute Departments of Applied Physics and Photon Science Stanford University and SLAC National Accelerator Laboratory)", "event_subtitle":"David A. Reis (Stanford PULSE Institute Departments of Applied Physics and Photon Science Stanford University and SLAC National Accelerator Laboratory)", "event_type":"Workshop \/ Seminar", "event_type_id":"21", "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\u2019ll present a novel method for studying non-equilibrium lattice dynamics in the time domain[1] which we\u2019ve 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\u2019ll show how we\u2019ve 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\u2013794, 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\u2013608, 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.", "occurrence_notes":null, "guid":"144106-21894670@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/144106", "building_id":"1000167", "building_name":"West Hall", "campus_maps_id":"163", "room":"340", "location_name":"West Hall", "has_livestream":0, "cost":"", "tags":["Physics","Science"], "website":"", "sponsors":[ { "group_name":"Department Colloquia", "group_id":"3804", "website":"" }, { "group_name":"Department of Physics", "group_id":"1965", "website":"" } ], "image_url":"", "styled_images":{ "event_thumb":"", "event_large":"", "event_large_2x":"", "event_large_lightbox":"", "group_thumb":"", "group_thumb_square":"", "group_large":"", "group_large_lightbox":"", "event_large_crop":"", "event_list":"", "event_list_2x":"", "event_grid":"", "event_grid_2x":"", "event_feature_large":"", "event_feature_thumb":"" }, "occurrence_count":1, "first_occurrence":21894670 } , "138848-21890501": { "datetime_modified":"20251202T115505", "datetime_start":"20260225T150000", "datetime_end":"20260225T160000", "has_end_time":1, "date_start":"2026-02-25", "date_end":"2026-02-25", "time_start":"15:00:00", "time_end":"16:00:00", "time_zone":"America\/Detroit", "event_title":"Grants office hours: Get support applying for one of SSC's Sustainability Grants!", "occurrence_title":"", "combined_title":"Grants office hours: Get support applying for one of SSC's Sustainability Grants!", "event_subtitle":"", "event_type":"Other", "event_type_id":"22", "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).", "occurrence_notes":null, "guid":"138848-21890501@events.umich.edu", "permalink":"http:\/\/events.umich.edu\/event\/138848", "building_id":"null", "building_name":"Off Campus Location", "campus_maps_id":"1", "room":"", "location_name":"Virtual", "has_livestream":1, "livestream_type":"other", "livetream_require_login":0, "livestream_id":"", "livestream_link":"https:\/\/meet.google.com\/hck-wekf-yci", "cost":"", "tags":["Environment","Sustainability"], "website":"https:\/\/planetblue.umich.edu\/campus\/get-involved\/for-students\/ssc\/grants\/", "sponsors":[ { "group_name":"Student Sustainability Coalition", "group_id":"4616", "website":"" } ], "image_url":"https:\/\/events.umich.edu\/media\/attachments\/2025\/09\/event_138848_original-1.png", "styled_images":{ "event_thumb":"https:\/\/events.umich.edu\/media\/cache\/event_thumb\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_large":"https:\/\/events.umich.edu\/media\/cache\/event_large\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_large_2x":"https:\/\/events.umich.edu\/media\/cache\/event_large_2x\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/event_large_lightbox\/media\/attachments\/2025\/09\/event_138848_original-1.png", "group_thumb":"https:\/\/events.umich.edu\/media\/cache\/group_thumb\/media\/attachments\/2025\/09\/event_138848_original-1.png", "group_thumb_square":"https:\/\/events.umich.edu\/media\/cache\/group_thumb_square\/media\/attachments\/2025\/09\/event_138848_original-1.png", "group_large":"https:\/\/events.umich.edu\/media\/cache\/group_large\/media\/attachments\/2025\/09\/event_138848_original-1.png", "group_large_lightbox":"https:\/\/events.umich.edu\/media\/cache\/group_large_lightbox\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_large_crop":"https:\/\/events.umich.edu\/media\/cache\/event_large_crop\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_list":"https:\/\/events.umich.edu\/media\/cache\/event_list\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_list_2x":"https:\/\/events.umich.edu\/media\/cache\/event_list_2x\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_grid":"https:\/\/events.umich.edu\/media\/cache\/event_grid\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_grid_2x":"https:\/\/events.umich.edu\/media\/cache\/event_grid_2x\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_feature_large":"https:\/\/events.umich.edu\/media\/cache\/event_feature_large\/media\/attachments\/2025\/09\/event_138848_original-1.png", "event_feature_thumb":"https:\/\/events.umich.edu\/media\/cache\/event_feature_thumb\/media\/attachments\/2025\/09\/event_138848_original-1.png" }, "occurrence_count":28, "first_occurrence":21884066 } }