Snapshot-FLASH

Snapshot FLASH pulse sequence Acquire echo... 

Neglecting T relaxation during the experiment, the total transverse magnetization is given by the sum of the amplitudes Mxo of the individual FID signals. For a snapshot-FLASH image of N lines, this is... 

Moment-aufnahme, /. instantaneous exposure or photograph, -bild, n. instantaneous photograph, snapshot, -klemme, /. instantaneous clamp, -ziinder, m. instantaneous fuse, detonator, -ziindpille, /. flash pellet primer, -zundung, /. instantaneous ignition or firing. 

Although the idea behind these femtosecond experiments is simple, the experimental setup to carry out the experiments is not at all trivial. In brief, it consists of a pulsed laser source capable of generating two femtosecond pulses of various duration (at the moment the world s shortest pulse is 6 femtosecond) a high vacuum chamber where a beam of molecules is flowing, and a sophisticated detector. A start laser flash called the pump pulse intercepts an isolated molecule in a molecular jet and sets the experimental clock at zero. A second flash called the probe pulse suitably delayed with respect to the pump pulse hits the same molecule and captures a photograph of the reaction in progress at that particular instant. Like the cameras in Muybridge s experiment, a femtosecond camera takes snapshots at different delay times to... 

The first successful experimental observation of the dynamics of the chemical bond was accomplished in the 1980s [2]. The clocking of such an ultrafast event requires an almost instantaneous initiation of the dynamics which can be accomplished by a femtosecond laser pulse. After this flash of electromagnetic radiation -the pump pulse - the dynamics of the induced photochemical reaction is probed via another ultrashort interaction with a probe pulse. This is repeated at various time delays between the pump and probe pulse and a series of snapshots are obtained which together constitute a molecular movie of the dynamics. 

There are 50 structures in the SDP. A few snapshots at different positions along the SDP are shown in Figure 13.5. The unfolding along this tube starts at the N terminaL It flashes on and off at the C terminal and finally progresses through the rest of the chain. 

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