Biomedical Engineering Reference
In-Depth Information
different isotopes of the same element are responsible for hyperfine structure in
the spectra of elements. As we mentioned at the end of Section 2.8, the existence
of isotopes has a big effect on the vibration-rotation spectra of molecules.
Nucleons are bound together in a nucleus by the action of the strong, or nuclear,
force. The range of this force is only of the order of nuclear dimensions,
∼10
-15
m,
and it is powerful enough to overcome the Coulomb repulsion of the protons in
the nucleus. Figure 3.1(a) schematically shows the potential energy of a proton as a
function of the distance
r
separating its center and the center of a nucleus. The po-
tential energy is zero at large separations. As the proton comes closer, its potential
energy increases, due to the work done against the repulsive Coulomb force that
Fig. 3.1
(a) Potential energy (PE) of a proton as a function of
its separation
r
from the center of a nucleus, (b) Potential
energy of a neutron and a nucleus as a function of
r
.The
uncharged neutron has no repulsive Coulomb barrier to
overcome when approaching a nucleus.
