Nuclear Physics and A. K. Jain

Lecture notes by Prof. A. K. JAIN, IIT ROORKEE CHAPTER 13: The Deuteron (Lecture time: 2 Hours) Deuteron is the simplest nuclear system where nuclear forces come into play. It is the “Hydrogen Atom” of nuclear physics. It may also be viewed as the simplest odd-odd nucleus, having one proton and one neutron. It exhibits features which require the use of a number of new concepts such as exchange force, tensor force etc. Of three possible states of two nucleon system, di-neutron, di-proton, and deuteron only deuteron is known to be stable. Since there are only two particles in the nucleus, the deuteron problem can be reduced to a one body problem in the center of mass frame and easily solved. We first discuss the various properties of deuteron. Properties of Deuteron It exists in its ground state only and has no excited states. Thus when energy is supplied to it, it readily disintegrates instead of going into higher energy states. Binding Energy: The binding energy of the deuteron is measured to be 2.22MeV . The measurements are carried out by using the atomic-mass spectroscopy and nuclear reactions. Two direct methods involve the slow neutron capture by proton  n  p  d    or, the inverse process i.e., the photo disintegration of deuteron. As the binding energy is very small, the deuteron is a loosely bound system. The depth of the potential well being 36MeV and the binding energy being 2.22MeV , it can be termed as a loosely bound system. It is almost sitting almost at the mouth of the potential and hence there is no excited state. Angular momentum and parity: The angular momentum J has been measured by a number of optical, radio frequency and microwave methods. The deuteron has J  1 angular momentum. Since the parity of the nuclear state cannot be measured directly, one uses the parity selection rules of nuclear disintegrations and reactions to determine the parity. An even parity thus emerges as the most 1

Lecture notes by Prof. A. K. JAIN, IIT ROORKEE

References: 1. R.R. Roy and B.P. Nigam, Nuclear Physics (Wiley Eastern, 1979). 9