# Binding energy

1. Nov 2, 2007

### nez

How can the time of binding energy be calculated?If so how long does it take to form deuteron nucleus?

2. Nov 2, 2007

### malawi_glenn

I would say that it is an instantanious process, scince only one gamma (photon) is emitted with 2.22MeV.

If one does the analogy with electrons in atoms, your question would also be "How long time does it get for an electron to be recombined to an ion" or "how long time does it get for the electron at n =3 to 'fall' to n = 1 level".

These are quantum states, and one should instead talk about the probability that a deutron is formed under certain circumstances (i.e. density of nucleons, temperature etc).

3. Nov 2, 2007

### Staff: Mentor

Or one could ask, how long does it take for a free neutron to bind with a proton to form a deuteron. Well - can make estimates based on our understanding of effective sizes of nuclei and use something like the speed of light or Heisenberg's uncertainty principle to provide a rough approximation.

But as malawi_glenn indicated, for all intents and purposes, it's instantaneous.

4. Nov 2, 2007

### nez

I will rephrase my question: According to liquid-drop model scientists have calculated the time(10 to the power of -14)sec for the first splitting of U-235 after being bombarded by neutron.How did they do it?

5. Nov 3, 2007

### malawi_glenn

That is a totally different question. From deutron formning to induced fission.

6. Nov 3, 2007

### nez

Sorry for misleading.The expression I know for calculation is
t=10^-21×10^7.85E sec, where E=19.0-0.36Z^2/A, but I couldn't get the answer (10^-14)sec!

7. Nov 4, 2007

### malawi_glenn

is it 10^(7.85E) or 10^(7.85) * E ? Be careful how you write formulas here.If I use the latter form, i got $$4.5\cdot 10^{-13} s$$

8. Nov 4, 2007

### nez

Thank you very much malawi glenn. I was looking for this answer. It was the book's printing mistake.