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

Microeconomics assignments, a severe restriction occurs to the availability...

a severe restriction occurs to the availability of consumer credit throughout the banking and finance system

Low standards of living, Low standards of living: In developing natio...

Low standards of living: In developing nations general standards of living tend to be very low for the vast majority of the people. These low standards of living are manifest

Budget constraints, Budget Constraints   * The Budget Line - The budg...

Budget Constraints   * The Budget Line - The budget line indicates all the combinations of 2 commodities for which total money spent equals the total income. * The Budget

Average cost curve, Why short run average cost curve is ‘U’ shaped

Why short run average cost curve is ‘U’ shaped

Find tax revenue, The US government decides to subsidize solar panels. For ...

The US government decides to subsidize solar panels. For each unit sold, the government pays $T to the buyer. Using a graph, show how this subsidy affects i) consumer surplus, ii)

Physical chemistry, Calculate the enthalpy change for stepE. that is for th...

Calculate the enthalpy change for stepE. that is for the reaction: Na(s)+ water (arrow) Na(ion)+ OH(ion)+ Hydrogen (g)

What do you mean by average product, Average product of a factor is the tot...

Average product of a factor is the total output produced per unit of the factor employed thus, Average product = total product / number of units of factor employed If Q stand

Graph questions, explain what will happen to price , the marginal cost of r...

explain what will happen to price , the marginal cost of rice, and the quantity produced if the government sets a production quota of 2000 bags a week. draw a graph and explain you

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