Neutron scattering lengths - Revision history

KevinYager: /* Neutron Scattering Length Density */

2015-01-20T17:22:02Z

‎Neutron Scattering Length Density

KevinYager at 19:40, 3 December 2014

2014-12-03T19:40:18Z

KevinYager at 13:56, 29 October 2014

2014-10-29T13:56:38Z

KevinYager: /* Neutron Scattering Length Density */

2014-06-14T15:46:11Z

‎Neutron Scattering Length Density

KevinYager at 16:42, 6 June 2014

2014-06-06T16:42:44Z

KevinYager: /* Scattering Length Density */

2014-06-06T06:31:01Z

‎Scattering Length Density

KevinYager: /* Scattering Length Density */

2014-06-06T06:18:17Z

‎Scattering Length Density

KevinYager: /* Scattering Length Density */

2014-06-06T06:16:17Z

‎Scattering Length Density

KevinYager: /* Origin of the scattering lengths */

2014-06-06T05:15:26Z

‎Origin of the scattering lengths

KevinYager: /* See Also */

2014-06-06T05:08:42Z

‎See Also

@@ Line 14: / Line 14: @@
 [[Image:SLD graph-water mixing.png|500px]]
-It is also noteworthy to compare this variation with the corresponding variation for x-ray interactions. Because x-ray interactions are governed by electron clouds, they increase roughly with atomic number (''Z''). This difference in behavior between x-rays and neutrons make the techniques highly complementary. For one thing, x-rays scattering most efficiently from high-''Z'' materials, whereas neutrons can be used on lighter atoms (e.g. soft matter containing mostly C and H). Studying a single system with both techniques also provides multiple contrast conditions, which makes data interpretation more robust.
+It is also noteworthy to compare this variation with the [[Atomic scattering factors|corresponding variation]] for [[x-ray]] interactions. Because x-ray interactions are governed by electron clouds, they increase roughly with atomic number (''Z''). This difference in behavior between x-rays and neutrons make the techniques highly complementary. For one thing, x-rays scattering most efficiently from high-''Z'' materials, whereas neutrons can be used on lighter atoms (e.g. soft matter containing mostly C and H). Studying a single system with both techniques also provides multiple contrast conditions, which makes data interpretation more robust.
 ==See Also==

← Older revision		Revision as of 19:40, 3 December 2014
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−	For ~~neutrons~~, the ''b<sub>i</sub>'' in the [[SLD]] equation are the [[neutron scattering lengths]] for the atoms in question.	+	For [[neutron]]s, the ''b<sub>i</sub>'' in the [[SLD]] equation are the [[neutron scattering lengths]] for the atoms in question.

	This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. (Of course, [[Origin of neutron scattering lengths\|there is an underlying reason]] for this.) This can be seen in the graphs below.		This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. (Of course, [[Origin of neutron scattering lengths\|there is an underlying reason]] for this.) This can be seen in the graphs below.

← Older revision		Revision as of 13:56, 29 October 2014
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−	For neutrons, the ''b<sub>i</sub>'' in the ~~above~~ equation are the [[neutron scattering lengths]] for the atoms in question.	+	For neutrons, the ''b<sub>i</sub>'' in the [[SLD]] equation are the [[neutron scattering lengths]] for the atoms in question.

	This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. (Of course, [[Origin of neutron scattering lengths\|there is an underlying reason]] for this.) This can be seen in the graphs below.		This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. (Of course, [[Origin of neutron scattering lengths\|there is an underlying reason]] for this.) This can be seen in the graphs below.

← Older revision		Revision as of 15:46, 14 June 2014
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	A common 'trick' in neutron experiments is to vary the ratio of H<sub>2</sub>O to D<sub>2</sub>O in the solvent; which allows one to vary the ambient SLD across a very wide range:		A common 'trick' in neutron experiments is to vary the ratio of H<sub>2</sub>O to D<sub>2</sub>O in the solvent; which allows one to vary the ambient SLD across a very wide range:
		+
	[[Image:SLD graph-water mixing.png\|500px]]		[[Image:SLD graph-water mixing.png\|500px]]

@@ Line 1: / Line 1: @@
 For neutrons, the ''b<sub>i</sub>'' in the above equation are the [[neutron scattering lengths]] for the atoms in question.
-This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. This can be seen in the graphs below.
+This value depends sensitively on the details of the nuclear interaction, and thus on the nuclear properties (spin, energy levels, etc.) of any particular nuclide (isotopic nucleus). Thus, the scattering length varies seemingly irregularly throughout the periodic table. (Of course, [[Origin of neutron scattering lengths|there is an underlying reason]] for this.) This can be seen in the graphs below.
 ====Neutron scattering length for Elements====
 [[Image:Output-elements.png|500px]]

@@ Line 7: / Line 7: @@
 [[Image:Output-combined.png|500px]]
-==[[Scattering Length Density]]==
+==Neutron [[Scattering Length Density]]==
 The neutron scattering lengths directly control the [[Scattering Length Density]] (SLD) of materials; i.e. the strength of neutron scattering from a given material. The wide variation of SLD for materials makes neutrons a uniquely powerful structural probe. On the one hand, one can vary the contrast condition simply by changing one isotope for another. For example, selective deuteration (of a material or a solvent) can be used to enhance a particular contrast, or to 'contrast match' a particular structure, thereby making it invisible to the neutron beam (and highlighting other structures). One can also attempt to, e.g., substitute one ion for an isovalent ion with a radically different SLD; or to perform the same experiment twice, with the substrate (or even just a layer in the substrate) swapped. The different contrast conditions allow for more robust data fitting (since a solution consistent with both datasets can resolve fitting ambiguities).

← Older revision		Revision as of 06:16, 6 June 2014
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	[[Image:SLD graph-water mixing.png\|500px]]		[[Image:SLD graph-water mixing.png\|500px]]

		+	It is also noteworthy to compare this variation with the corresponding variation for x-ray interactions

	==See Also==		==See Also==

← Older revision		Revision as of 05:15, 6 June 2014
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	[[Image:SLD graph-water mixing.png\|500px]]		[[Image:SLD graph-water mixing.png\|500px]]

−
−	~~==Origin of the scattering lengths==~~
−	~~The following description is adapted from [www.ncnr.nist.gov/programs/sans/pdf/polymer_tut.pdf Boualem Hammouda's (NCNR) SANS tutorial].~~
−
−	Consider a neutron of energy <math>E_i</math> interacting with a nucleus, which exhibits an attractive square well of <math>-V_0</math>; where <math>V_0 \gg E_i</math>. The [http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation Schrödinger equation] is:
−	~~:<math>~~
−	~~\left[ \right] = E \psi~~
−	~~</math>~~

	==See Also==		==See Also==

← Older revision		Revision as of 05:08, 6 June 2014
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	[[Image:SLD graph-water mixing.png\|500px]]		[[Image:SLD graph-water mixing.png\|500px]]

		+
		+	==Origin of the scattering lengths==
		+	The following description is adapted from [www.ncnr.nist.gov/programs/sans/pdf/polymer_tut.pdf Boualem Hammouda's (NCNR) SANS tutorial].
		+
		+	Consider a neutron of energy <math>E_i</math> interacting with a nucleus, which exhibits an attractive square well of <math>-V_0</math>; where <math>V_0 \gg E_i</math>. The [http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation Schrödinger equation] is:
		+	:<math>
		+	\left[ \right] = E \psi
		+	</math>

	==See Also==		==See Also==