In this article, we will discuss Yukawa’s Meson theory of Nuclear Forces. The mechanisms responsible for the strongly attracted nonelectric, non-gravitational short-range forces were given by Yukawa in 1935.
He predicted the existence of a new particle now called pi-meson, having a rest mass greater than that of an electron but less than that of the nucleon.
He proposed a theory of nuclear forces that involves these pi-meson’s & is known as Meson- theory of Nuclear forces.
According to this theory, all nucleons(protons & neutrons) consists of an identical course surrounded by a cloud of one or more pi -mesons.
The mesons may be neutral or may carry a positive charge or a negative charge and are denoted by π °, π +, π- respectively.
The mesons are continuously exchanged between a neutron and a proton which generate the exchange process i.e. nuclear forces.
When a π+ meson jumps from a proton to a neutron. The proton is converted into a neutron and neutron is converted into a proton.
p — π+ ~~> n
n + π+ ~~> p
Conversely, when a π- meson jumps from a neutron to a proton the neutron is converted to a proton & proton is converted into a neutron.
n — π- ~~> p
p + π- ~~> n
An exchange of π ° protons is converted into protons & neutrons are converted into neutrons.
p ± π° ~~> p
n ± π° ~~> n