The radial probability density for the hydrogen ground state

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Discussion Overview

The discussion centers on the experimental verification of the radial probability density for the hydrogen ground state, as presented in introductory texts. Participants explore various experimental techniques, including x-ray scattering and electron scattering, and the challenges associated with observing hydrogen in such contexts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire about experimental verifications of the radial probability density for hydrogen, referencing introductory texts.
  • Several participants suggest that x-ray scattering could be a method to probe the radial probability density.
  • One participant notes that hydrogen atoms are often invisible in x-ray studies of periodic structures due to interference from other atoms with more electrons.
  • A participant mentions a recent experiment related to hydrogen's orbital structure, expressing surprise at the lack of awareness among knowledgeable individuals in the forum regarding basic issues in the field.
  • Another participant discusses the momentum space distribution of molecular hydrogen determined by electron scattering spectroscopy, suggesting that similar studies may exist for atomic hydrogen but are challenging to conduct.
  • Some participants caution against taking popular articles at face value, emphasizing that what is observed is electronic density rather than orbitals, and highlight the accuracy of high-precision x-ray crystallography in mapping electronic density.
  • There is mention of the difficulty in creating a pure flux of atomic hydrogen for experiments, which complicates the use of x-ray scattering.
  • One participant points out that while transition probabilities for hydrogen are well-known and experimentally verified, the connection to the radial wavefunctions remains uncertain.

Areas of Agreement / Disagreement

Participants express differing views on the reliability of popular articles regarding hydrogen's orbital structure and the methods for observing hydrogen. There is no consensus on whether existing experiments confirm the radial probability density as described in introductory texts.

Contextual Notes

Participants highlight limitations in the experimental approaches, including the challenges of observing hydrogen in various contexts and the distinction between electronic density and orbital visualization.

ftr
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You can probe it e.g. using x-ray scattering.
 
DrDu said:
You can probe it e.g. using x-ray scattering.

thanks. Do you know any reference please.
 
Do you know some example? I heard that hydrogens are usually invisible in X-rays of periodic structures (metals, proteins), probably due to the fact that other atoms have much more electrons and re-radiate much stronger radiation which thus overshines the radiation due to hydrogens.
 
Jano L. said:
Do you know some example? I heard that hydrogens are usually invisible in X-rays of periodic structures (metals, proteins), probably due to the fact that other atoms have much more electrons and re-radiate much stronger radiation which thus overshines the radiation due to hydrogens.

It is quite strange, I asked this question for a particular reason I had, it turns out that the answer involves an experiment done only few days ago!


http://io9.com/the-first-image-ever-of-a-hydrogen-atoms-orbital-struc-509684901

I am also surprised that there are a lot of people who know physics on PF (many seem to be professionals), but they are not aware of these basic issues.
 
The momentum space distribution of molecular hydrogen has been determined by electron scattering spectroscopy:

http://pubs.acs.org/doi/abs/10.1021/ja00332a017?journalCode=jacsat

This rather directly gives the Fourier transform of the r-space distribution. It is possible that atomic hydrogen has been studied by the same technique, but I suspect not, due to the difficulty of maintaining a pure flux of atomic hydrogen.

Edit: Correction, it has been done for H as well - ref. on page 1 of the above article!
 
ftr said:
It is quite strange, I asked this question for a particular reason I had, it turns out that the answer involves an experiment done only few days ago!

This is a popular article and you should not believe everything written in it. First you don't see the orbitals but at best the electronic density. The electronic density can be mapped accurately e.g. with high precision X-ray crystallography (also for compounds containing hydrogen), so it is certainly not the first time "orbitals" have been observed.
I was thinking of X-ray scattering in the gas phase on hydrogen atoms. This is certainly demanding (as gadong pointed out it is difficult to create a flux of atomic hydrogen, but possible) and I don't know whether it has been performed. The experiment cited by gadong is very similar to my idea, only that it uses electron scattering and not x-ray scattering.
 
DrDu said:
This is a popular article and you should not believe everything written in it. First you don't see the orbitals but at best the electronic density. The electronic density can be mapped accurately e.g. with high precision X-ray crystallography (also for compounds containing hydrogen), so it is certainly not the first time "orbitals" have been observed.
I was thinking of X-ray scattering in the gas phase on hydrogen atoms. This is certainly demanding (as gadong pointed out it is difficult to create a flux of atomic hydrogen, but possible) and I don't know whether it has been performed. The experiment cited by gadong is very similar to my idea, only that it uses electron scattering and not x-ray scattering.

The article is based on this paper


http://prl.aps.org/abstract/PRL/v110/i21/e213001

I guess they are saying that their measurement is "more" direct.

All that aside, I still cannot find out if these experiments confirm the radial functions in the OP. I guess I will have to dig deeper on my own.
 
DrDu said:
This is a popular article and you should not believe everything written in it. First you don't see the orbitals but at best the electronic density. The electronic density can be mapped accurately e.g. with high precision X-ray crystallography (also for compounds containing hydrogen), so it is certainly not the first time "orbitals" have been observed.

Excited orbitals?
 
  • #10
The transition probabilities for hydrogen are very well known and experimentally verified. The calculation for the transition probabilities are based on the dipole matrix for the orbitals, which depends on the radial wavefunctions.
 

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