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

Describe customer-firm relationship, Question 1: "The rush of new and e...

Question 1: "The rush of new and existing enterprises to exploit the opportunities presented by the internet economy is giving rise to new business models". Discuss. Ques

Monopoly, how is monopoly different from opligopoly

how is monopoly different from opligopoly

Is economic development is based on goverment, Is economic development is b...

Is economic development is based on goverment Many governments--mainly unelected governments-aren't that interested in economic development. Giving valuable industrial franchis

Price elasticity of supply, Price elasticity of supply – Computes the p...

Price elasticity of supply – Computes the percentage change in quantity supplied resulting from a 1 percent variation in price. – The elasticity is usually positive as price

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

Theory of supply, how to make attractive assignment on theory of supply

how to make attractive assignment on theory of supply

Cost theory, if marginal cost descreases then what else is effected by this...

if marginal cost descreases then what else is effected by this

What is economics, What is Economics?  Economics is explained as the s...

What is Economics?  Economics is explained as the study of how people choose to use their scarce resources in an attempt to satisfy their unlimited wants. In other words, we h

World trade organization, World Trade Organization: An international econom...

World Trade Organization: An international economic organization based in Geneva, Switzerland,formed in 1995 which is dedicated to promoting greater trade and investment among its

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