22.08.2015   Nuclear and Radiochemistry

Analytical Methods Using Irradiations with Neutrons

As discussed in Section 5.5.3, the interactions of a neutron with matter are defined by its neutrality, the magnetic momentum, and the de Broglie wavelength (about 1010m). The most characteristic interactions are the nuclear reactions and the scattering phenomena. The analytical methods involving neutrons utilize the following characteristics of neutrons:

• Having no charge, neutrons can be captured easily by the different atomic nuclei. Except for helium, all atoms can capture neutrons, a fact that makes them ideal for analytical purposes.

• Neutrons interact with the nuclei, and light and heavy elements can be analyzed at the same time.

Irradiation

Method

Thickness of the Studied Layer

Typical

Sensitivity

Primary Information

Detectable Elements and Species

Photon

NMR

Bulk

—

Chemical state of bulk and adsorbed molecules

Magnetically active nuclei (with lh spin isotopes,

b80)

ESR

Bulk

—

Electron structure

Paramagnetic species

IR, NIR

0.5—2.5 pm

0.1—0.5%

Bonding geometry and strength of bulk and adsorbed molecules

Functional groups

Visible, UV spectroscopy

0.1 pm

0.001 —1000 ppm

Elementary and molecular analysis

Li—U

UPS, XPS (ESCA)

3 nm

0.1%

Species, surface elemental composition, valency, chemical bond

Li—U

LAMMA

0.5% inorganic; 0.1 —10 ppm organic

Microelement and molecular analysis

Na—U

AES

1 nm

0.1%

Elemental composition, adsorbate analysis

Li—U

EXAFS, XANES, NEXAFS

50 nm

500 ppm

Oxidation state, species, coordination number, some structure

Li—U

XRF

XRD

104nm

104nm

1 — 10 ppm

Chemical composition of bulk and near surface region Structure of bulk and surface, mineral composition

Na—U

Mossbauer

Bulk

1 — 1000 ppm

Site locations, structure, bonding, chemical environment

Isotopes with Mossbauer transitions

Electron

Electron diffraction, including LEED and RHEED

1 nm

Identification of microcrystalline phases

Li—U

(Continued)

Irradiation Method

Thickness of the

Typical

Primary Information

Detectable Elements and

Studied Layer

Sensitivity

Species

AES

1 nm

0.1%

Elemental composition, adsorbate

Li—U

analysis

SAM

1 nm

0.1%

Elemental composition, adsorbate

Li—U

103 nm

analysis

EMP

0.1%

Chemical composition of bulk

Na—U

and near surface region

EELS

100 nm

<0.1%

Elemental composition, species

Li—U

like IR, bonds, structure

SEM

5 nm

Surface and bulk morphology

TEM

Surface and bulk morphology

Ion ISS

1 — 100 pm

100 ppm

Elemental composition, location

Li—U

of adsorbed species

SIMS

3 — 10 nm

0.1 —10 ppm

Elemental, isotopic, and

H—U

molecular composition

IMMA

3— 10 nm

0.1 —10 ppm

Elemental, isotopic, and

H—U

104 nm

molecular composition

CPINRA

0.1 —10 ppm

Elementary composition

IEX, PIXE

104 nm

0.1 —10 ppm

Elemental composition, location

Na—U

104 nm

of adsorbed species

IMXA

0.1 —10 ppm

Elementary composition

RIBS

103 nm

0.01—1%

Elemental composition, location

Li—U

of adsorbed species

Neutron NAA

Bulk

0.001—0.1 ppm

Elemental analysis of bulk

Li—U

PGAA

Bulk

0.001—0.1 ppm

Elemental analysis of bulk

H—U

Neutron scattering

Bulk

Structure and morphology

SANS

Bulk

Structure and morphology

Nuclear reactions

Bulk

0.001—0.1 ppm

Elemental analysis of bulk

Li—U

Source: Adapted from Nagy and KOnya, with permission from Taylor & Francis.

• Neutrons have magnetic moments. The scattering methods based on the interaction of the neutrons with the nuclei and the magnetic field of matter provide information on both the nuclei and the magnetic field.

• The information obtained is on a molecular scale because of the very short de Broglie wavelength of neutrons.

• The energy of the neutrons can vary widely and can be compared to the energy of atomic and molecular motions.

• The range of neutrons is fairly large; thus, microscopic properties of bulk phases can be studied, even in industrial sizes.

• Neutrons are indestructible: biological, archeological, criminal, and other kinds of sam­ples can be analyzed without destruction.

The application of neutrons in the natural sciences was discussed in Section 5.5.3. The different types of NAA and neutron scattering will be discussed

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