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October 7th, 2020 | Company News

What is Time-Resolved Electron Microscopy?

Electron microscopy (EM) is a powerful imaging technique renowned for its outstanding spatial resolution. It surpasses the theoretical maximum resolving power of conventional microscopy by several orders of magnitude, enabling researchers to probe nanoscale structures and to resolve the chemical composition of samples with unprecedented precision. However, standard EM systems are typically unsuited to monitoring the change of macromolecular structures over time. For that, researchers must employ time-resolved electron microscopy.

 

A Brief Introduction to SEM & TEM

Before delving into the basics of time-resolved electron microscopy, it is worthwhile outlining the basic working principles of EM.

Conventional microscopy uses visible light to magnify objects/surfaces up to a theoretical maximum of 1000x. This so-called resolving limit is imposed by the wavelengths of visible light. Electrons have much shorter wavelengths than light which is detectable by the human eye. In fact, an electron beam can be used to magnify objects up to an unprecedented 200,000x with exceptional degrees of chemical specificity.

There are two main types of EM: scanning electron microscopy (SEM), and transmission electron microscopy (TEM). These differ in the way that samples are illuminated, but each one uses the same basic apparatus to generate a focused electron beam which is directed onto the object of interest. They differ in that an SEM uses a series of deflector coils to alter the beam path and raster scan the sample, while a TEM uses a fluorescent screen to generate a projection image. Each of these systems tends to use a continuous wave (CW) electron beam, which cannot provide relevant temporal data.

Factoring in Time Resolution

Although many critical dynamics and structures can be investigated using traditional SEM or TEM, it is often important to analyse systems at more stringent timescales. Time-resolved electron microscopy is employed where researchers need to correlate their spatial data with ultrafast temporal resolution. This solution has been developed as a direct result of relatively recent advances in laser technology, particularly in the field of ultrafast pulsed wave (PW) laser systems. Femtosecond laser technology – with ultrashort pulses and high repetition rates – is the leading solution for this space.

The basic principle of operation for time-resolved electron microscopy systems involves the irradiation of a sample with short electron pulses which capture rapid snapshots at specific intervals, determined by the length of these electron beam pulses. Most time-resolved electron microscopy electron beams feature pulses approaching the femtosecond regime, providing detailed insights into sample composition, dynamics, and structure with both high spatial and temporal resolution.

Time-Resolved Electron Microscopy Solutions

Laser Quantum is a world-leading manufacturer of ultrafast laser sources for demanding areas of application. We offer time-resolved electron microscopy solutions based on our own proprietary ultrafast laser systems. If you would like to learn more about using femtosecond lasers for time-resolved EM, why not contact a member of the team today?



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