I read about cryo-electron microscopy but the articles I could find were relatively old. And as someone out of the field I could not decide if this was really the current case. Any comments with corresponding references will be highly appreciated.
The main question is what do you want to do. Electron microscopy is a wide field. There are different types especially developed for very specific applications and therefore very limited in use, or the typical "workhorses" which are easy in use but less good in resolution. Please note that the resolution given by manufacturers are always related to very special setups of the microscopes, often far away from the application you want use. Analytical microscopes are commonly not that high resolving since you need as many as possible electrons and they are less easy to control than only a few passing the electron optical system at the same time. An additional factor is the invironment where the microscope is running, i.e. electromagnetic fields, temperature variations, mechanical vibrations. Especially for long-time experiments like any type of mapping this is an essential and often underestimated problem. And don't forget: sample is not sample. Electrons are charging objects. Even metals are not ideal conductors...and you need to mount then somewhere.
The main question is what do you want to do. Electron microscopy is a wide field. There are different types especially developed for very specific applications and therefore very limited in use, or the typical "workhorses" which are easy in use but less good in resolution. Please note that the resolution given by manufacturers are always related to very special setups of the microscopes, often far away from the application you want use. Analytical microscopes are commonly not that high resolving since you need as many as possible electrons and they are less easy to control than only a few passing the electron optical system at the same time. An additional factor is the invironment where the microscope is running, i.e. electromagnetic fields, temperature variations, mechanical vibrations. Especially for long-time experiments like any type of mapping this is an essential and often underestimated problem. And don't forget: sample is not sample. Electrons are charging objects. Even metals are not ideal conductors...and you need to mount then somewhere.
An accurate answer requires many clarifications but I can give you some hints about the case of transmission electron microscopy (scanning electron microscopes have worst figures).
Overall, the resolution that you can get depends on the technique used, the equipment and the sample. State-of-the art microscopes with aberrations correctors and extra bright field emission guns can resolve routinely single atoms except Hydrogen, so the spatial resolution is below 1 angstrom (10-10 meters).
In terms of time resolution 99% of the miscroscopes are limited by the sensitivity of the sensors. It is of the order of milliseconds when you aquire spectra or tens of 100 of ms for images but you most likely have bad signal to noise ratio.
New detectors, like windowless x-ray spectrometers and direct CMOS and backilluminated CCD cameras are improving rapidly temporal resolutions. For example Gatan a camera manufacturer for TEM sells K2, a direct CMOS camera than can acquire hundreds of frames per second. But again the maximum speed that you can get will be limited by you sample and experimental conditions.
Finally, it is worth mentioning the new field of 4D electron microscopy (check google) , a amazing stroboscopic method using electrons that permit attaining temporal resolutions of ps with atomic resolution. This new microscopes are not commercially available yet.
If the question is really about cryo-electron microscopy and not microscopy for radiation-hard materials then quoting the ultimate instrument performance would be a bit misleading. For radiation sensitive-materials such as proteins, the maximum radiation dose is in the range of 20 electrons per square Angstrom (or 2000 per nm^2). In this case, the signal-to-noise ratio is not all that good, especially when the particle is embedded in amorphous ice, and one often turns to techniques such as 'single-particle analysis' (SPA). SPA, for example, actually takes thousands of pictures of identical molecules to stitch together the atomic positions in the molecule (if that...). Some of the SPA results are controversial, as Henderson goes over 'Einstein from noise' potential pitfalls here:
http://www.pnas.org/content/early/2013/10/08/1314449110
So for cryo-electron microscopy of biological molecules, the state of the art may be around 0.5 nm, which is still not quite 'atomic', and even so, potentially controversial. As the direct-electron detectors and (perhaps) Zernike phase plates make their way into common use then performance may continue to improve.
Some major principles in the field to search for are: Glaeser, Henderson, Mao, Zhaung, Frank, and Zhou.
Dear all,
many thanks for your answers. Definitely the field is very wide and naming and ultimate resolution is not possible. I am not directly using electron microscopes. I am an accelerator physicist and we are developing a new electron source in the University of Manchester. What we do is to trap a cloud of neutral atoms and then after ionising the atoms to extract the electrons as a beam. The reason I needed some information as it seems either energy spread or emittance (a measure of electrons diffusion in the angle-position space) can be controlled nicely. I wanted to know a set of challenging specifications and then make sure our system can produce it...
Here is a short summary of what we have: http://lanl.arxiv.org/pdf/1406.0756.pdf
Regards, Oznur
Spatial resolution as low as 0.5 Angstrom is routinely achieved today in HRTEM. Temporal resolutions of nanoseconds can be achieved nowadays with Dynamic TEM in certain conditions.
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