The Naked Scientists

The Naked Scientists Forum

Author Topic: Can the particles of Helium be observed?  (Read 2341 times)

Offline Atomic-S

  • Hero Member
  • *****
  • Posts: 928
  • Thanked: 18 times
    • View Profile
Can the particles of Helium be observed?
« on: 25/01/2015 04:49:42 »
Is there any way to simultaneously observe the positions of the nucleus of a helium atom and also the positions of its two electrons?


 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1872
  • Thanked: 143 times
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #1 on: 25/01/2015 04:55:59 »
I don't think it's possible to get sub-atomic resolution like that--at least not by any method I know of or could even imagine...
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4107
  • Thanked: 245 times
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #2 on: 25/01/2015 05:50:08 »
Heisenberg's uncertainty principle says that you cannot precisely measure the position of anything (and the less massive the object, the harder it gets). What's worse, the process of measuring it renders the measurement obsolete!

To measure the position of a Helium nucleus, you could use something like gamma rays. But gamma rays are so energetic that bouncing a gamma ray photon off a Helium nucleus will move that nucleus away from the position it held when you measured it.

Electrons are much less massive than a Helium nucleus, and the uncertainty in position is spread out over a larger area - in fact, the size of a whole Helium atom. You could attempt to measure the position of an electron with an electron beam, but these are so energetic that they would knock the electron right out of the atom.
 

Offline PmbPhy

  • Neilep Level Member
  • ******
  • Posts: 2760
  • Thanked: 38 times
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #3 on: 26/01/2015 08:45:01 »
Quote from: evan_au
Heisenberg's uncertainty principle says that you cannot precisely measure the position of anything (and the less massive the object, the harder it gets). What's worse, the process of measuring it renders the measurement obsolete!
That's a common misunderstanding of the uncertainty principle. Uncertainty applies only to an ensemble of measurements, not to individual measurements. You can measure the position of a particle exactly. What you can't do is keep repeating it and expect to get the same result when the measurement is made of identically prepared systems.
 

Offline Atomic-S

  • Hero Member
  • *****
  • Posts: 928
  • Thanked: 18 times
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #4 on: 27/01/2015 04:17:46 »
I  would be thinking in terms of determining the positions to an accuracy of about 1% of the radius of the atom.
 

Offline alancalverd

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 4704
  • Thanked: 153 times
  • life is too short to drink instant coffee
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #5 on: 27/01/2015 07:28:25 »
And there's the problem. The more accurately you know the position of something, the less accurately you know its momentum, so the moment after you found its position, it may be somewhere else. 
 

Offline evan_au

  • Neilep Level Member
  • ******
  • Posts: 4107
  • Thanked: 245 times
    • View Profile
Re: Can the particles of Helium be observed?
« Reply #6 on: 27/01/2015 10:38:46 »
Quote
Is there any way to simultaneously observe the positions of the nucleus of a helium atom and also the positions of its two electrons?
The Schroedinger Equation allows you to calculate the probability of finding the electrons of Helium atom, relative to the nucleus.

The mathematics is rather complex to solve, but computer techniques have improved to the point where computers can now model the (outer) electron structure of some fairly complex molecules (an achievement which earned the Nobel prize for chemistry in 2013).

 

The Naked Scientists Forum

Re: Can the particles of Helium be observed?
« Reply #6 on: 27/01/2015 10:38:46 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums