the microscope on the basis of atoms

[alkis3]

why electron microscope uses electrons

when the de Broglie waves 0.01 nm energy of the electron = 7000 Electronvolt

 

 

if the electron, replace the uranium atom, at a wavelength of 10 nm, the power of the atom will amount to 0.01 Electronvolt

0.01 Electronvolt is not dangerous for the studied material

 

why is it not used?

[studiot]

 

why electron microscope uses electrons

 

Because if it used a different particle it would not be an electron microscope.

 

This is not a facetious answer, perhaps you do not know that there are many types of microscope?

 

For example the Field Ion micdorscope uses larger particles than electrons.

 

The optical microscope uses particles that, as far as I know, do not constitute a health hazard.

 

So what are you actually trying to say?

 

[alkis3]

as I know, the main problem of obtaining high resolution in the electronic microscope it is the de Broglie waves

for an electron it is too big

if the electron will have little wave,he'd have more energy

big energy to destroy the investigated object

 

if you use a heavy atom ,then this problem will be solved

and the resolution of the microscope is < 100 pm

 

or I make a mistake?

[John Cuthber]

There are several issues.

Firstly, people use hydrogen and helium ions in place of electrons.

http://en.wikipedia.org/wiki/Field_ion_microscope

and they do that for the reasons you have given.

Also, if you use heavier particles they tend to damage the surface you are looking at.

[Schneibster]

The easy answer is because the uranium atoms still have the same momentum, and it is momentum that is conserved in the interaction between the probing beam and the substrate being probed.

 

However, there is also a microscope called the "atomic force microscope" in which the atoms do not move and therefore have both the short wavelength you mention, plus no motion of a beam so not much momentum, and for some purposes these are very useful. Look up "AFM" and "atomic force microscope." I think there's a pretty good Wikipedia article on it.

[alkis3]

well,imagine 2 ball,the first has a mass of 1 kg second 2 kg

the speed of 1 m/s and its momentum 1*1=1 and its energy 1*(1*1)/2=0.5

 

the second speed = momentum/ mass
1/2=0.5 his energy when this speed is 2*(0.5*0.5)/2=0.25

as we see the momentum of the first and second equal ,then an equal and wave

but the energy of the first 2 times more than the second.

why the second can ionize atoms as well as the first if they have different energy?

 

if calculated elastic collisions of particles with the same momentum

it turns out that if the electron will strike in electron,the second electron will fly up with speed of 1800 km/s

if proton hits the electron,the electron will fly at a speed of 2 km/s

these calculations with the same impulse

Edited April 7, 2014 by alkis3

[Schneibster]

What "speed?"

 

It's a needle, probing a surface. The needle comes to a point that is a single atom.

 

You see where it starts experiencing van der Waals forces from the surface. It never actually touches it.

[CharonY]

What "speed?"

 

It's a needle, probing a surface. The needle comes to a point that is a single atom.

 

You see where it starts experiencing van der Waals forces from the surface. It never actually touches it.

 

That is the ideal case, though rarely are tips that fine in reality. Also, depending on the type of surface (especially soft, irregular ones, like biological specimen), the tip can easily get into contact with the surface (e.g. due to inevitable delays of the feedback loop and piezo).

Also in contact mode the attractive forces are strong enough so that there is a sudden movement of the tip (the snap-in) to the surface. Again, depending on the surface properties and the set point, the tip can be in physical contact with the sample.

 

It is also important to note that AFMs have much higher resolution in the z-axis (0.1-1 nm in the best cases), whereas lateral resolution is much poorer and for irregular substrates also prone to certain artifacts (but then so are all microscopic techniques, at least when it comes to biological specimen).

[Schneibster]

All correct. I worked with an autofocus expert who worked on AFMs.

 

Thing is, if it touches any of those ways you messed up and you usually have to start over, and that's if you didn't damage the sample or the probe and need to replace them. So it's a key point to keep the probe from touching the sample.

[Enthalpy]

If using atoms instead of electrons, the size of these atoms limit the resolution - to about one atom. This is an other limit than the wavelength.

 

Electron microscopes use energies well over 7keV and achieve resolution little better than one atom. The limit for them is more the poor quality of the "lenses", as well as the available intensity in very small areas.

 

You might consider protons, deuterons, alphas instead. But as a drawback, they give more momentum to the atoms they hit, making a bigger damage.