Nuclear Physics What is nuclear physics In general

Nuclear Physics

What is nuclear physics? • In general, nuclear physics is the study of any process occurring in the nucleus • Spontaneous decay • Nuclear reactions • Fission: a large nucleus is broken into two smaller nuclei • Fusion: two or more smaller nuclei are ‘stuck’ together to form a larger nucleus • Both of these reactions produce energy as a byproduct!

Spontaneous decay? ? • A nucleus is radioactive if it spontaneously changes its atomic or neutron number • All elements above 83 are radioactive! • Radioactive decay is caused by the nuclear weak force

What is alpha decay? • Parent nucleus loses four nucleons: two protons and two neutrons • The parent turns into the daughter by emitting an alpha particle • Really just a helium nucleus • Massive and low energy • A sheet of paper can stop an alpha particle!

What is beta decay? • Two types: beta-plus, where a proton turns into a neutron and betaminus, where a neutron turns into a proton • Mass number doesn’t change, but atomic number goes up OR down one! • The parent turns into the daughter by emitting a beta particle • Negative beta particle is just an electron and a positive beta particle is a positron • Smaller mass than an alpha particle and higher energy • Would go through paper, but 3 mm of aluminum will stop a beta particle!

What is gamma decay? • The nucleus doesn’t change, it just throws out pure energy in the form of photons • Always occurs AFTER an alpha or beta decay – the nucleus has too much energy and just ‘gets rid’ of it • The nucleus emits a gamma particle • Really just photons with a frequency in the ‘gamma ray’ part of the EM spectrum • No mass and extremely high energy • Need 60 cm of aluminum or 7 cm of lead