Video Captions Supporting Video 1. Ultrafast electron microscopy (UEM) bright-field video of picosecond photoinduced strain-wave dynamics in multilayer MoS2. Video of picosecond intralayer and interlayer strain-wave dynamics in differently-oriented sections of an MoS2 flake. The intralayer modes appear as propagating contrast waves in the relatively thicker (darker) crystal region generally to the left of the frame, while the interlayer modes appear as bend contours oscillating about a fixed spatial position in the thinner region generally to the right of the frame. Each UEM image was acquired with a 20-kHz repetition rate and a 30-s acquisition time per frame. The video illustrates dynamics at 1-ps steps spanning -15 to 305 ps. Time zero (i.e., the t = 0 ps frame) is the experimental time zero (the time at which dynamics are first observed, not necessarily the time at which photoexcitation occurred).
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