Difference in binding energies

[rp8308]

if i calculate the change in binding energy in a decay process such as B-decay using SEMF, and then i calculate the same difference in binding energy using the difference in atomic masses and electron masses. why are they different?

 

[mathman]

The binding energy is the difference between the masses of the nuclei - the electron masses don't enter into the calculation.

 

[Bob S]

The binding energy is the difference between the masses of the nuclei - the electron masses don't enter into the calculation.

See the thread

https://www.physicsforums.com/showthread.php?t=333491

The neutral 163Dy atom is stable, but it has a beta decay half life of 47 days when all the atomic electrons are stripped off.

See
"ound-state -decay was experimentally observed for the very first
time at the [CERN] heavy ion storage ESR . For this pilot experiment a striking example
has been chosen: 163Dy, which is stable as a neutral atom because the Q-value for
continuum -decay to 163Ho is negative, Qc = −2:56keV, might decay as a bare ion
by b-decay to the ground state of 163Ho with a positive Q-value of roughly 50keV
for the electron being emitted into the K-shell of the daughter atom. This decay
has indeed been observed and the measured half-life of (48+5
−4)d agrees nicely with
the theoretically expected half-life of 50d ."

in page 14 of

http://cdsweb.cern.ch/record/410569/files/ep-99-165.pdf

Bob S

 

[mathman]

I learned something new. It still doesn't address the original binding energy question.

 

[Bob S]

I learned something new. It still doesn't address the original binding energy question.

In the case of 163Dy and 163Ho, neither the difference in atomic masses nor the difference in nuclear masses (using semi-empirical mass formula) predict that the 163Dy atom or the bare 163Dy nucleus is radioactive, after accounting for the decay beta mass. But 163Dy is radioactive anyway, only because the decay beta final state is the bound 1s atomic state of 163Ho (about 61 KeV). So electron mass and the atomic electron binding energies (including the atomic binding energy of the decay beta) sometimes play a key role in determining whether a nucleus is stable.

Bob S

 

[mathman]

What about ordinary radioactive decay (atoms just sitting around)?