The lecture on nuclear properties is posted. Please provide comments and questions related to this lecture. The homework on the final page can be returned by e-mail or submitted during the next class meeting on this lecture, Tuesday 3-September-13.
Dr. Czerwinski, on slide 2-7 it says that the alpha decay for Am is 5.48 and 5.44 MeV but using the Q values it come out to be 5.638, I was just wondering how you got 5.48 and 5.44 is that based on the mass excess, delta=M-A for each one?
ReplyDeleteGreeting.
ReplyDeleteThe point is that the Q value is not the same as alpha decay. The Q value is the total energy of the system. This includes the recoil of the alpha, which is the alpha decay energy, as well as the daughter. Also for alpha decay we can get a few different energy values from the same isotope. This is because the parent can alpha decay to an excited state in the daughter, which de-excites to the ground state with gamma emission.
The bottom line is that the Q value is very close to the alpha decay energy. During the lecture on alpha decay we will discuss the equations one can use to calculate alpha decay energy from the Q-value. We will show how you can use this in models to calculate the alpha decay half life.
We will learn more about Q-value in upcoming lectures.
alright then thank you
DeleteThis lecture was very clear in describing Q-values and the liquid drop model
ReplyDeleteWhen calculating Q values, there are several 212Bi listed here:
ReplyDeletehttp://www.nndc.bnl.gov/nudat2/wcbyz.jsp?z=83
How do we determine which to use?
You should use the mass excess for 212Bi. The data is:
Delete212
83 Bi
0.0000 1(-) -8.1201 60.55 m 6 β- : 64.06 %
α : 35.94 %
. The mass excess is -8.1201 MeV
I've listened to the lecture but I have a question on your Q value example. On slide 4 of Lect 2, you have Na-24 as having 23.99 amu, where is that information from? The Chart of Nuclides has Na-22 as having 22.99 amu but I didn't see the amu for Na-24.
ReplyDeleteThe mass was found from one of the web links listed on the lecture page. The data for 24Na mass can be found at http://www.nndc.bnl.gov/masses/mass.mas03 and at the Q value calculator site. For the Q value calculator if you just enter an isotope decay q values and mass data will be provided.
DeleteAfter finishing Lecture 2, I was confused on slide 2-6 under Positron Decay in the example. It states that the 90-Nb yields 90-Zr+, but if there is supposed to be an extra electron from the daughter, shouldn't the charge be negative? I wasn't sure if it was a typo or if I had missed something.
ReplyDeleteCorrect Aaron, it should read Zr-, this is a typo. The correct generalized equation is at the top of the page.
DeleteI just finished lecture 2.
ReplyDeleteI have finished lecture 2
ReplyDelete