FEI has launched the Tecnai Femto ultrafast electron microscope (UEM), enabling scientists to explore events and processes that occur at the atomic and molecular spatial scale .
Fundamental processes that happen over time spans measured in femtoseconds include the absorption of light energy and its transformation into heat or mechanical changes (photoactuation) and the crystallisation or recrystallisation of materials–including large biological molecules for structural analysis.
The Tecnai Femto is the first system to commercialise the patented ultrafast electron microscopy technology pioneered by Nobel laureate Prof. Ahmed Zewail at the California Institute of Technology. The first Tecnai Femto UEM will be installed at the University of Minnesota this month.
“This is a truly revolutionary technology,” stated Trisha Rice, FEI’s vice president and general manager of the Materials Science Business Unit. “Until now, the only commercially-released instruments that could look at processes at this time scale were limited to observations of bulk materials.
“The Tecnai Femto UEM is the first to combine femtosecond time resolution with nanometer spatial resolution, allowing researchers to see the structural changes that occur at the atomic scale in response to the energetic stimuli.”
The Tecnai Femto is a member of FEI’s Tecnai family of transmission electron microscopes (TEM). It has been modified to accommodate ultra short laser pulses that stimulate a brief ’flash’ of photoelectrons from the electron source, and a precisely-timed pulse of laser energy directed at the sample as a stimulus.
To achieve the highest temporal resolution when observing reversible processes, the Tecnai Femto UEM operates in stroboscopic mode where a large number of precisely-timed flashes, each containing as few as a single electron, build up a representative image of the sample at a given delay between stimulus and flash.
The delay is then adjusted incrementally and another image acquired, resulting ultimately in a sequence of images much like the frames of a motion picture.
For irreversible processes, such as fractures, the instrument can be operated in the single pulse mode with many electrons in the pulse, but unlike the femtosecond single-electron mode, the time resolution reaches picoseconds to nanoseconds because of Coulomb repulsion. Importantly, the instrument can also be operated in conventional continuous-beam TEM mode.
