This lecture discusses alpha decay in radionuclides. Theories on alpha decay are presented. Systematics and energetics involved in alpha decay are presented. The correlation between Q value and decay energy is described. The Geiger Nuttall relationship is provided, described, and utilized in a model for alpha decay. Tunneling is also exploited to described alpha decay, coupling energy and half-life. Gamow calculations are shown to reflect the Geiger Nuttall relationship. Hindered alpha decay is discussed. Hindered alpha decay is employed to described nuclear properties. Hinderance factors are described, along with how they are calculated and where they can be found. Proton and other charged particle emission are presented.
I was looking at the slides and I think there's a typo on the 5th slide which has to do with energetics of U-238 alpha decay. There is a transposition of 4.270 to 4.720; the math is correct though.
ReplyDeleteyes, that is correct. I will make the change. bonus points for the catch.
DeleteI just submitted the quiz! There was a question about alpha decay of 246Pu, but the chart of nuclides does not list an alpha decay for this isotope. Is alpha decay possible for 246Pu?
ReplyDeleteit is. If we could shut off the beta decay it would be observed. The alpha decay probability is just much less than the beta decay probability. You could actually use the half life to estimate the percentage of decay that goes by alpha.
DeleteWhen discussing alpha decay theory, it was said that an atom might beta decay to the energy minimum on a mass parabola, and then alpha decay to a different A value in order to conserve spin and parity. These refer to the quantum mechanical wavefunctions from physical chemistry, right? How would we know whether spin/parity would be conserved, or is that something you would need to look up?
ReplyDeleteThe quantum is the same, some slightly different rules between electrons and nucleons. This will be evident at the shell model. Nucleons can occupy state that are not allowed for electrons, say 1f for nucleon. Generally we think of these terms as conserved. The general rule is transitions with the same multiplicity are spin-allowed. If the multiplicity changes the transitions are forbidden. This will be evident in the beta decay lecture.
DeleteI had the same confusion thank you for clearing it up.
DeleteI found it very fascinating how you could relate the half life of alpha decay to the rate of quantum tunneling...
ReplyDeleteThis is a terrific example for tunneling.
DeleteIs the discussion of tunneling related to Hawking radiation, or are they separate concepts entirely?
ReplyDeleteThe concepts are different, but rely upon the same quantum mechanics. A good discussion of Hawking radiation and tunneling can be found at: http://www.physics.umd.edu/grt/taj/776b/fleming.pdf
DeleteAre helium and alpha particles completely synonymous? Or is there a reason that alpha particle is used more often? Is it purely due to the alpha, beta, gamma trend of the alphabet?
ReplyDeleteUsing He usually implies an atom, electrons included. The alpha particle does on have electron upon emission.
ReplyDeleteThe answers and comments to PDF Quiz 4 are now posted. There is some information and question 4, tunneling, that may need review. The concept of the question was to relate increased energy with a decrease in barrier.
ReplyDelete