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Chapter 4. Particle scattering
cident particle before and after the scattering event is preserved.
This phase coherence enables the study of a crystalline target
through electron diffraction.
A separate example of nearly elastic scattering is the Coulomb
scattering of an energetic alpha particle by a heavy nucleus. This
is the mechanism originally used by Rutherford [59] to characterize
an atomic nucleus as a compact, massive, multiply charged body.
In elastic scattering, the magnitude of the momentum of the incident particle is unchanged by the scattering, but the direction can
be significantly changed. Consequently, significant momentum can
be transferred.
Alternatively, the incident particle can transfer significant energy
to the target. Such an event is known as inelastic scattering. This
is much more complex than elastic scattering, because a rich variety of secondary processes can result. For example, an incident
fast electron can excite the electronic states of a target material,
giving rise to an excited-state atom, secondary photon, free electron, electron-hole pair (exciton), or plasmon. Performing electron
energy loss spectroscopy on the scattered electron yields information on the chemical and physical nature of the target material.
Separately, the resulting secondary electron current forms the basic contrast mechanism in the scanning electron microscope, or
a scanning helium ion microscope. Alternatively, bombarding a
material with an ion beam causes secondary ions of the target
material to be ejected. Performing secondary ion mass spectrometry gives direct information about the atomic composition of the
target material.
Separately still, an incident electron or ion beam can be used to
chemically alter a target polymer film in a useful way. The patterned film is then used as a binary mask in the process known as
lithography. A focused electron beam or a focused helium ion beam
can form a very fine, sharp writing pencil. Lithographic structures
down to a few nanometers in size have been produced by this
Chapter 4. Particle scattering
cident particle before and after the scattering event is preserved.
This phase coherence enables the study of a crystalline target
through electron diffraction.
A separate example of nearly elastic scattering is the Coulomb
scattering of an energetic alpha particle by a heavy nucleus. This
is the mechanism originally used by Rutherford [59] to characterize
an atomic nucleus as a compact, massive, multiply charged body.
In elastic scattering, the magnitude of the momentum of the incident particle is unchanged by the scattering, but the direction can
be significantly changed. Consequently, significant momentum can
be transferred.
Alternatively, the incident particle can transfer significant energy
to the target. Such an event is known as inelastic scattering. This
is much more complex than elastic scattering, because a rich variety of secondary processes can result. For example, an incident
fast electron can excite the electronic states of a target material,
giving rise to an excited-state atom, secondary photon, free electron, electron-hole pair (exciton), or plasmon. Performing electron
energy loss spectroscopy on the scattered electron yields information on the chemical and physical nature of the target material.
Separately, the resulting secondary electron current forms the basic contrast mechanism in the scanning electron microscope, or
a scanning helium ion microscope. Alternatively, bombarding a
material with an ion beam causes secondary ions of the target
material to be ejected. Performing secondary ion mass spectrometry gives direct information about the atomic composition of the
target material.
Separately still, an incident electron or ion beam can be used to
chemically alter a target polymer film in a useful way. The patterned film is then used as a binary mask in the process known as
lithography. A focused electron beam or a focused helium ion beam
can form a very fine, sharp writing pencil. Lithographic structures
down to a few nanometers in size have been produced by this