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

Production, explain the concept economies/diseconomies of scale and minimum...

explain the concept economies/diseconomies of scale and minimum efficient scale

Discrimination, Discrimination: As a result of sexist and racist attitudes ...

Discrimination: As a result of sexist and racist attitudes and deliberate efforts of employers to oppose groups of workers against each other, different groups of people (divided a

Representative consumer faces a wage income tax, suppose, as in the federal...

suppose, as in the federal income tax code for the united states, that the representative consumer faces a wage income tax with a standard deduction. That is the representative con

Compare traditional modern and engineering cost theory, compare traditional...

compare traditional modern and engineering cost curves

Derive the linear demand and supply, Suppose that the short-run world deman...

Suppose that the short-run world demand and supply elasticities for crude oil are -0.076 and 0.088, respectively. The current price per barrel is $30 and the short -run equilibrium

Long-run supply of housing , The Long-Run Supply of Housing * Scenario...

The Long-Run Supply of Housing * Scenario 1: Owner-occupied housing - Suburban or rural areas - National market for inputs * Questions - Is this an increasing or co

Define the policies of education - US Economy, Define the Policies of Educa...

Define the Policies of Education Universal education--particularly universal education of girls--pays a two-fold benefit. Investments are more likely to be productive with a be

Draw and label demand curve for a cup of coffee for consumer, Suppose the d...

Suppose the demand curve for a consumer for coffee is: Q = 6 - 2P, where Q represents the number of cups per day and P is the price of coffee per cup.  1.  Suppose the con

Demand and supply considerations of education, Normal 0 false ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

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