Neutron diffraction, chemistry, Microeconomics

Assignment Help:

chemistry assignmentsNeutron diffraction supplements x-ray diffraction and is particularly helpful in locating hydrogen atoms.

An x-ray beam is scattered primarily as a result of interaction with the electrons that surround each atom of an ion or molecule. Thus the atomic scattering factors are approximately proportional to atomic numbers. As a result, it is difficult to locate low atomic number in the presence of high atomic number atoms. Thus the position of hydrogen atoms generally cannot be deduced from x-ray diffraction studies. (A positive attitude to this difficulty is the recognition add to the complexity of many already complex structure determinations.) Within a factor of 3 or 4, all nuclei or, more conveniently, deuterium nuclei can be located in the presence fo behavior atoms.

Neutron diffraction is also distinguished by the noticeable role of the magnetic moment of the neutron when diffraction occurs from crystals with ordered atomic magnetic moments. Neutrons diffraction can be used to study the orientation of atomic magnetic moments in ferromagnetic and antiferromagnetic crystals. Neutron diffraction is thus a specialized adjunct to z-ray diffraction.

A neutron beam is usually formed from the thermal neutrons of a nuclear reactor. A velocity selector device augmented by crystal diffraction provides a monochromatic beam. The wavelength associated with the neutron beam can be calculated from the de Broglie relation. The momentum term mv is obtained for thermal neutrons by setting

½ mv2 = 3/2 kT

And rearranging to get;

Mv = √3mkT

With appropriate numerical values, including 1.675 × 10-27 kg for the mass of a neutron, we obtain,

1.46 ×10-10 m = 146 pm

A beam of thermal neutrons therefore has a wavelength suitable for diffraction studies of crystals. A diffraction pattern like those obtained for x-ray diffraction except that a longer wavelength beam is used is obtained.

Typically crystals, whose structures are known, except for the postions of hydrogen atoms, are studied. The transform procedure is used that the positions fo these remaining nuclei are found. The smallness of the nuclei would lead to sharp peaks on a nuclear density map, but thermal motion produces some spreading of these peaks. 


Related Discussions:- Neutron diffraction, chemistry

Elasticities of demand:, price of laptop increases by 20% and there is a 40...

price of laptop increases by 20% and there is a 40% drop in the quantity demanded?

Microeconomic analysis, what is the theory of Second best? Prove the theore...

what is the theory of Second best? Prove the theorem with the help of a diagram.

What factors shift the aggregate demand curve to right, What factors shift ...

What factors shift the Aggregate demand curve to right and what factors shift the AD curve to left?  AD shifts to the right when any component of AD enhances autonomously; e.g

What are the policies and long-run growth of us, What are the Policies and ...

What are the Policies and Long-Run Growth In many concerns it is decidedly odd that world distribution of output per worker is as unequal as it is. Migration, World trade and f

Production possibility frontier, Halala is a small country that uses most o...

Halala is a small country that uses most of Its resources to produce fruits and vegetables. If the country produces only fruits it is able to produce 8000kg of fruit per year. If i

Managerial theories of firm., Implications of Williams model of managerial ...

Implications of Williams model of managerial discretion in Nepalese industries

Least square methods, The least square method is based on the assumption th...

The least square method is based on the assumption that the past rate of change of the variable under study will continue in the future. It is a mathematical procedure for fitting

Determine the economic productivity level, Determine the economic productiv...

Determine the economic productivity level Up until 1500 as best we can tell there had been next to no growth in output per worker for the average human for millennia. Even in 1

Limitations of Valence Bond Theory, Valence Bond Theory Explains, but does ...

Valence Bond Theory Explains, but does not predict the shape. Valence Bond Theory Cannot explain colour and spectra. Valence Bond Theory Qualitative explanations; does not expl

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd